Of the more recent highly rated films (not sure they're classics, but...):
Casino Royale - James Bond plays poker for an hour, followed by an exciting action sequence where James Bond...sits in his car nearly choking on a drink, before getting better, just in time to allow him to...continue playing poker for another hour. Then suddenly loads of buildings collapse and for some not adequately explained reason one of the characters gets electricuted and wheeled away at the end. Seriously what was this? It was one of those times you watch a film purely on the recommendation of others then are forced to come to the conclusion that everyone except you is an idiot.
Avatar - For some reason it being in 3D seemed to make everyone overlook what a terrible film it was. I found the problem was that at the start of the trailers it was like "3D yeah, wooo. this is amazing!", then by the time the film started "3D, woo, yeah", then by 20 minutes into it "actually, this is a bit shit"...then it seemed to carry on for another 6 hours or so. Afterwards I had a headache due to being exposed to natural light after wearing darkened 3D glasses for hours.
Forest Gump - It wasn't that I didn't like it, just, I didn't really get what the point in any of it was...and I can't remember like the entire last half of the film because I always get bored and stop paying attention at around the same point.
Inception - This will probably be unpopular. It was ok, but, here's some cool things my dreams often include that don't appear in this film: sex, flying, pirates, big massive lava explosions, robot spiders, general absolute mental surrealness, etc.
Here's some things I never dream about that were in this film a lot: rooms with nothing happening in them, people walking about in suits, walking, people unecessarily explaining things, sitting around, entirely normal looking buildings, meetings, etc.
Also the spinning top bit at the end was the most predictable ending to any film ever.
