God... people need to see a wider variety of films IMO (as in: older, foreign).
Best:
Once Upon a Time in the West
The Seven Samurai
Jaws
Raiders of the Lost Ark
The Shawshank Redemption
Worst: (Oh, where to begin...)
Anything Megan Fox was in.
Anything Quentin Tarantino wrote.
Boondock Saints. It fucking sucked. I know it, you know it. Stop perpetuating the myth.
Torture-porn "films". Saw and Hostel fans, I'm looking at you...with pity.
Anything with a frat-boy mentality. Including movies starring/written/directed by, but not limited to: former SNL cast members, Dane Cook, that-guy-who-wrote-Superbad, the American Pie cast (including Allison Hannigan. Damn you, Willow, damn you...). I'd also include all of the parody movies like Scary Movie, Epic Movie, et al.
My ONE exception is The Hangover, but that's only because I've been a fan of Ed Helms since The Daily Show and Zach Galifianakis since he wore a pink tutu and danced to The Bangles "Eternal Flame" during a stand-up bit about 10 years ago. God, that was pure win. Still, The Hangover wasn't that funny.
<< Yeah, I'm rather a movie snob...