Haha, it all depends on my mood.
I'm really not a movie snob, and I watch pretty much any genre. Basically, I watch almost any movie that's considered 'good', and I watch any movie that's considered crap if it's popular just so I have a basis for discussion. For example, I'm thought Avatar and Transformers 2/3 were all crappy, but I watched them so I can discuss them with my friends. I also try to watch all the Oscar best picture nominees so that I can have a gauge of the difference between critics' taste and mine.
In terms of my favorite movies: Nausicaa, Laputa, Old Boy, Battle Royale, Casino. I'm really really into stuff from Studio Ghibli, and I find that I rewatch their films the most.
To me, a movie is supposed to be entertaining first and foremost. I can only stand to watch a documentary if the storytelling is entertaining while educating.