Some good ones here.
The postman, but also I liked Waterworld. Yes, his characters are wooden. I enjoyed the movies.
I liked Popeye, but I guess that if I saw it again I wouldn’t.
Stargate.
Starship Troopers.
Joe vs the Volcano.
I notice that all but one are cheesy sci-fi movies. I just don’t think that the reviewers like that stuff.
Rat Race is the funniest movie I have ever seen. I saw it in the cinema when it came out (I was about 11 years old) and have watched it countless times on DVD since. Oh god it is hilarious.
Rent, Spice World, Who’s That Girl? and Purple Rain are some others that were reviewed poorly/have a bad reputation but I love them.
My two favourite films are The Rocky Horror Picture Show, which was savaged by critics when it came out but of course is now considered a classic, and Titanic, which obviously wasn’t considered a bad movie when it first appeared but it is very uncool to admit liking now.
Stealth.
Because, well…you ever see a movie just because an actress (or actor) you like is in it? And possibly wearing a whole lot of nothing at some point?
Well, Stealth had a damned sexy aircraft. And Jessica Biel wearing a bikini in one scene, which was frankly just a bonus.
Oh, and one more…GI Joe: The Movie. The animated one, from 1987.
As far as I can tell, I’m the only person in the world who liked this movie, and the plot premise. Possibly including the screenwriters. 
Ok, I’m gonna play my master card here:
C.H.U.D.
Very Bad Things. Dark comedy, everything goes wrong…I just like it.
Boondock Saints. Pure vigilante porn with bad Irish accents and lots of scenery chewing by Willem Defoe. But I like it. The sequel tried too hard to capture what made the first so good, though, and failed. Or perhaps didn’t quite succeed.
Wild Things got a 64% (fresh) from critics at RT, but only a 53% (rotten) from viewers, so I guess it only partly fits the OP’s criteria, but is one of my go-to guilty pleasure movies.
K-19 (mentioned upthread) likewise comes in at 60% fresh, but I like it quite well, too. It’s a refreshing (and IMO, much more realistic) portrayal of professional military sailors (regardless of nationality) than most modern submarine films achieve, and it doesn’t try for a sappy, feel-good ending; just a sort of ambiguous, “Well, we survived it, and here we are” ending that, also IMO, is much more realistic.
Please, it’s the latest in communication technology.
Tommy Boy and Toys were two of my favorite movies for a while. I also love the movie I.Q., although I hated it when I first saw it in the theater.
I love cheesy movies!
Tremors – all four of them!
Independence Day
Starship Troopers
A Knight’s Tale
someone mentioned Run, Lola, Run above – I show that every year to my German classes, and they’re always open-mouthed as they watch this surreal masterpiece
I love it. Could do with less shrieking Willie and less kid, of course. But on the whole, it’s awesome.
I also used to adore Toys - I’d like to see it again. I remember LL Cool J being hilarious.
Pootie Tang, which despite being written and directed by Louis C.K. and starring Chris Rock and Wanda Sykes, with a cameo by Bob Costas, currently has a Rotten Tomatoes approval rating of 27%.
It makes me happy to see some love here for Joe Versus The Volcano. Sadly underrated movie.
I, too, thought this movie was hilarious. I expected it to be terrible but it was one of the funnier movies I saw last year. (I didn’t see the British version either).
Of course he did, he actually is from another planet!
I don’t mind “Lucky # Slevin” aka ‘the wrong man’ (tomatometer 51%), don’t mind the whole tarantino wannabe.
Surprised nobody’s mentioned “Glitter”. Yeah, it wasn’t “The Godfather”, but it wasn’t trying to be. It’s also my understanding that the movie strayed from what Mariah originally envisioned. It’s biggest problem? Released 2 weeks after 9/11.
Red Dawn, of course. Got awful reviews when it first came out, and it’s cheesy as hell, but I loved it. Since then, it seems to have developed a cult following.
D.C. Cab, for the cheeserific performances by Mr. T and Gary Busey.
Mars Attacks! also got bad reviews when it came out, but again, brings the sweet, smelly cheese!
Freddy Got Fingered - seen it dozens of times. This movie is a dadaist masterpiece.
Meet The Fockers, also seen at least two dozen times, though many of those were just as background noise to fall asleep to.
Breakfast of Champions - critically panned, though it had a great cast and I thought it was a good attempt at adapting the source material.
The Postman - Will Patton steals the show as one of the best villains ever.
Ebert did not care for The Usual Suspects either. One of my favorites…
His original review: clickety
Quite a lot of some of my fave films have been mentioned in this thread already, I’ll add some more to the pile:
Constantine - oh my god, the jaw dropping special effects! And I’m a complete atheist and it made ME want to go to church afterwards!
The time machine - with Guy Pearce. Even my own beloved Film Brain pissed on this movie and had virtually nothing good to say about it, but I really love it and (incidentally enough) so has everyone I’ve ever watched it with.
I’m at the point now where other people’s opinions of films (especially critics considering how much they dislike things that I enjoy) is pretty much entirely incidental to my enjoyment of a movie. If I’m in a cinema watching a film and every single person in there hates it except me, then so what?
I think it’s wonderful fun with beautiful Art Direction, right up to the point where Jeremy Irons shows up, when it all turns into a big pile of WTF.