My nomination for the “What! Nobody Mentioned?” musical is A Funny Thing Happened on My Way to the Forum. You know, back when Stephen Sondheim wrote songs with melodies. 
“Springtime For Hitler”! Oh wait…
In no particular order:
West Side Story
1776
Brigadoon
My Fair Lady
The Music Man
Very, very difficult to confine my list to five, but these are probably the ones I’ve watched most and have nearly (or completely) memorized.
I finally got around to watching SITR over the holiday and, huh? What is the big deal? I expect the villagers with torches to be along any moment but my word that movie was dull!
Amongst my top picks (most of which have already been mentioned by others but so what) are: Wizard of Oz; Top Hat; Flying Down to Rio; Gilda (hey, Rita Hayworth sings, it’s a musical); Hedwig; Moulin Rouge!; Summer Stock (I’m a sucker for a good tractor-riding number); oh I could go on but now I have so many songs running through my head I may need Thorazine.
Best musical in the last 20 years Southpark: bigger, longer, and uncut, probably best ever too 
Another vote for West Side Story, a hearty second to South Park, and how has no one mentioned The Sound of Music? Sure, it’s overexposed, but that’s because it’s good.
I’m a big fan of the more recent generation of broadway musicals… I’d love to see Les Miz or Rent filmed… I’m psyched that Phantom of the Opera will be hitting the big screen soon…
What, no votes for Mary Poppins? For shame.
Cabaret
Oliver!
Hedwig and the Angry Inch
Willy Wonka and the Chocolate Factory
Umbrellas of Cherbourg
- Singing in the Rain
- Wizard of Oz
- Cabaret/Chicago (tied due to Fosse)
- West Side Story
- Hedwig/Tommy (tie)
I would’ve also done the Siging in the Rain as 1-5, but West Side Story and Oz I picked more for their cinematic cultural significance (ie/ you know they’re important when they are parodied so damn often).
Interesting to see that Evita hasn’t really made anyone’s top five.
My Fair Lady
Singin’ in the Rain
Fiddler on the Roof
Moulin Rouge
Chicago
Not necessarily in that order.
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Singin’ in the Rain. It really is the best ever; just the opening credits put a big stupid grin on your face that doesn’t go away. The coolest part is it’s a musical that manages to be hip and corny at the same time.
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Moulin Rouge. I’ve heard people complain that they copped out by not doing original music, which seems to be missing the point. It’s such a spectacular bit of movie-making; the scene of them dancing on clouds above Paris with the moon singing to them is what movie musicals are all about.
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High Society. Grace Kelly is smokin’ hot. And Louis Armstrong & his band as the chorus puts it over the top.
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The Band Wagon. Cyd Charisse is also smokin’ hot. And she gets to do more in this one in than in An American in Paris. I’m not a huge fan of this one, really, but included it in the same way you include Citizen Kane in best-of lists – it’s just (along with Singin in the Rain) one of the definitive movie musicals.
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The Little Mermaid. Why wouldn’t Disney movies be included in these lists? Musicals are supposed to be corny and overly sentimental. The music is great – I listened to it in college without shame – and the lyrics are still really, genuinely clever.
My honorable mentions would go to Fantasia, An American in Paris, and Willie Wonka and the Chocolate Factory. And dishonorable mention goes to Dancer in the Dark for taking brilliant music and turning it against me in one of the worst movies I’ve ever seen.
Well, if we’re going to count filmed stage performances than Sunday in the Park with George wins hands down with me, no contest. (which interestingly hasn’t been mentioned yet despite mention of at least 3 other Sondheim works in this thread thus far).
I’ll add to that:
- The Rocky Horror Picture Show
and second Willy Wonka… and JCS.
And since no one’s mentioned it yet, I’ll add Singin’ in the Rain
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The Music Man (the Robert Preston/Shirley Jones version, NOT that dreadful Disney crap released last year)
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Singing In The Rain
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The Sound Of Music
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West Side Story (the best musical from a composition standpoint, but by no means my favorite)
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Fiddler On The Roof
Some other time my list might be different, but those are the ones that come to mind right now. I’m pretty sure my number one pick will always be The Music Man. I see it about once a year, and enjoy it every time. It’s just one big smile of a film. Makes me feel good.
In no particular order:
Sound of Music -
Music Man - nearly perfect movie musical…and my goodness, the choreography. Still beyond amazing.
Top Hat
West Side Story - which I really don’t love, but I’ve got to put it on the list.
Beauty and the Beast - also a nearly perfect movie musical…so what that they were animated.
Honorable mention - Chicago, Sweet Charity, Hedwig, Easter Parade (I love it. I don’t care what anyone says, I love that movie), Oliver!
Personally, and in no particular order:
The Music Man (the Robert Preston version, and not, ahem, the Matthew Broderick one…what were they thinking… :smack: )
Chicago (yes, it was recent. yes, it was excellent)
Into the Woods (Sondheim is a genius)
TOMMY (I wasn’t around for the 70s, but I have played the pinball game)
1776 (somewhat obscure, but very well done)
Why, no my movie-watching experience is not that broad, why do you ask?
My criteria for determining favorite musicals is ‘Will I sing straight through this every time I watch it?’ Using that as a guideline:
Top Hat (although the “Continental” number in The Gay Divorcee is my favorite Fred&Ginger piece; the movie is only about an hour-and-a-half long, and this number takes up more than 20 minutes of it).
Cabaret
Beauty and the Beast
Gigi
The Wizard of Oz
A Hard Day’s Night
Actually, Rocky Horror fits this criteria too.
Does The Blues Brothers count? It’s an interesting survey piece featuring blues, rock, soul, and gospel, mixed in with car chases.
White Christmas - Danny Kaye is a criminally underappreciated singer/dancer/comedic actor.
Love’s Labours Lost - Shakespeare, Gershwin, Branagh; what more could you ask?
The Sound of Music
The Wizard of Oz
Animal Crackers - hurray for Captain Spaulding!
I may as well post my list:
- Singin’ In The Rain
- Mary Poppins
- White Christmas
- West Side Story
- South Park (You have to admit, the composition was first rate)
I hate, hate, hate Cabaret. And Grease, God help us all.
I’m writing this without reading the threads so as not to be influenced, and all of course are strictly my imho. It’s amazing how completely different my answers are than if you’d asked “top five Broadway musicals” (which would be a cool thread for somebody else to start just to compare notes):
IN NO PARTICULAR ORDER
1- 1776-
One of the best musicals ever done also qualifies as one of the best movies ever made about American history, musical or otherwise. The characterizations are near perfect, at once showing the men of the Continental Congress as living, breathing, admirable and flawed mortals but without needless bashing of the sort so often done by academics desperately seeking name recognition, and the love song twixt John & Abigail (taken almost entirely from their real life letters) is one of the most beautiful and sweetly erotic songs ever to appear in a motion picture (all the more spectactular considering it’s sung by two over-30 actors you have no desire to see nekkid). The gamble of bringing the B’way cast, none of whom had ever had starring roles in a movie with a budget this major (Daniels’ supporting role as Hoffman’s father in THE GRADUATE was probably the biggest claim any of them had) may not have paid off at the box office, but it most certainly paid off by making the movie immortal (and if when I can get to the afterlife I find out Benjamin Franklin does not sound like Howard DaSilva I’m going to fire off an angry letter).
2= EVITA
Probably a controversial choice, but I actually liked this movie. While in some ways I thought the production was a bit prosaic, there were moments that worked beautifully, such as the morph between illegitimate peasant girl Evita banned from her father’s funeral and Evita’s own funeral (only 20 years later) at the beginning. The decision to give Madonna “Another Suitcase in Another Hall” may initially have been just to give her more screentime and soundtrack time, but it worked, and the way they subtly insinuated prostitution with the slow tango montage worked much better than the stage version (in which her sleeping her way to the top is seen as almost unbroken and instantaneous), and who knew Antonio could sing like that? Plus, using the balcony of the real Casa Rosada totally and successfully exploited the advantages of celluloid over stage.
3- Fiddler On The Roof
What on Earth can you say about this movie that hasn’t been said a million times? Topol IS Tevye, Paul Mann IS Lazar, and even the “way too old for the role” Leonard Frey was perfect in retrospect.
4- Scrooge-
I’ll admit one reason that I’m placing this one on here is because nobody else will probably and I’ve always thought it was underrated. The duet sung twixt the young/hopeful Finney-as-Scrooge and the old-futureless Finney-as-Scrooge worked beautifully, the romantic songs were lovely, the Ghost of Christmas Present’s song is irresistably joyous, and this remains my favorite ever telling of the Christmas Carol.
5- The King and I
The book on which it is based is almost totally fabricated, the plot is at best P.I. by our standards and at worst outright racist, Brynner is the dream of every third rate impersonator, and the depiction of East Meets West couldn’t even take place in the same universe as MISS SAIGON, but when Yul begins swinging Deborah and there’s more silk flying than on Cleopatra’s barge, I just don’t care!
Honorable Mention: Best Little Whorehouse in Texas- Dolly, Charles Durning, Robert Mandan and even Jim Nabors were so perfect in their roles that you could almost forgiven the horrible miscasting of Dom Deluise in a role that’ve been better played by a Robert-Duvall-as-over-the-top-Jimmy-Swaggartish character and the presence of Burt Reynolds (who is, admittedly, at his least annoying in this movie, being as it was before he made the shift from everybody’s obnoxious smug playboy brother-in-law to everybody’s obnoxious and unbearably embittered former playboy brother-in-law).
My votes for FIVE WORST MOVIE MUSICALS (with less commentary):
CAMELOT- Richard Harris was a great actor, Vanessa Redgrave was/is a great actress, the score and libretto were good and England would seem a logical choice to film, but they seemed to have forgotten any sense of fun or frivolity from the stage version or the fact that maybe just maybe it’d be good idea to cast more than one person with a nice singing voice.
MAN OF LA MANCHA- Compared to this movie “LAST TANGO IN PARIS” must have seemed like “the feel good comedy of the year!”
GIGI- even I’m not gay enough for this one (though I do love Hermione Gingold in anything- ever read her autobiography, HOW TO GROW OLD DISGRACEFULLY ? )
MAME (Lucy’s becoming less a wacky redhead than a henna haired mummy right in front of our eyes, she’s about as sophisticated as a gas station urinal, she’s been doing the same schtick on screen more than a decade after its expiration date and the original non-musical is an impossible-to-improve on classic that was still in recent memory at the time, but what have we got to lose?)
AT LONG LAST LOVE (wtf?)