I've got to agree with Spiff on Zoolander. My wife and I were less than impressed the first time we watched it as I think our expectations were too high. But I have watched it countless times since on cable and that movie really grows on you. The 2001 Space Odyssey spoof with the computer is a classic scene.
Dude, Where's My Car also grew on me the more times I watched it on cable. Not the finest piece of cinema ever, but it's pretty funny.
Twisting this around, a darling of the critics that I thought was terrible was The Hours. Shows what they know.
