This came to me when I was answering another thread. There have been many great movies, but a lot of them have been as a result of one or more (usually more) acting performances that made the film great.
I was thinking of films where the movie was great (or very good), but you would be hard pressed to say the main actors played a star role.
My first nomination (and there will be more): The Thirty Nine Steps
Nah, without Robert Donat it would have been much worse, IMO. Madeleine Carroll was nothing to write home about, though. Well, her performance, anyway. 
I’ll nominate… Sullivan’s Travels and 2001: A Space Odyssey.
I though the red blinking light was magical as HAL.
I think a lot of great horror, sci-fi and action flicks (though certainly not all) are able to get away with this. The Matrix and Star Wars leap to mind.
King Kong (unless you count the monkey)
Au Hasard, Balthazar (unless you count the donkey)
Playtime
The Red and the White
2001: A Space Odyssey
Battleship Potemkin (and most other Russian silents: Earth, Man With a Movie Camera, Strike, October, etc.
Un Chien Andalou & L’Age D’Or too
Weekend & Two or Three Things I Know About Her
**The Travelling Players
Tabu
The Birds
Freaks
Dawn of the Dead
**
Surely Lord of the Rings has an ensemble cast…
No. I submit that a real actress would have ruined the film. The fact that Tippi Hedren couldn’t act her way out of a paper bag is crucial to the pervading sense of surrea uneasiness in the film.
Wow, awfully defensive on Tippi when I didn’t even mention her name. I don’t mind Tippi, but that doesn’t mean she, or anyone else, is “stand out”.
And Sullivan’s wouldn’t be the same without Sullivan–Joel McCrea is certainly more critical to his film than Donat is to the Hitchcock above.
What I meant was that Hedren stands out as being mediocre, thus making the film. IMHO, of course.
As for McCrea, I dunno. I think he could have been replaced by Muni or Cooper. Obviously, IMHO.
Joe vs The Volcano: The luggage salesman. Wow.
Or am I missing the point of this thread?
Yep, I see I misread the thread title and then misunderstood the OP.
So, um, nevermind…
Good call on The Matrix. Let’s face it: all of the acting in that movie is pretty damn wooden. It’s the concept and the storytelling that sell the movie.
How about Highlander? Christopher Lambert doesn’t bring anything special to the role of Conner MacLeod. (Certainly not a believable Scottish accent 
)
Freaks
Slight hijack…
Was the midget who started the “one of us” chant in Freaks the same midget in Beyond thunderdome? Master Blaster
Gattaca.
yes! i own Freaks on DVD, and that was in the special features
Oh, Jude Law. Disagree.
Koyaanisqatsi. 
I think The Cruel Sea would qualify. It was more the grimness of the film than any stand out performances.