Hmm. This is a bit of a hard one.
In no particular order:
The Hitchhiker's Guide to the Galaxy
The Ultramarines Movie
Also, all six Star Wars movies. Because they're all pretty epic.
I'll probably pick up flak for liking the Ultramarines Movie, as it was generally regarded as not very good. But it's also the only 40K movie around, so I like it anyway.
And AVATAR, which I just loooooove to hate.
This. Because I hate that movie on principle. I mean really, a bunch of spear-toting natives beat down an interstellar-capable civilization? Do they not realize just how stupid that is?
Because any real interstellar civilization wouldn't have bothered with the natives. They'd just wipe 'em out, and then claim all the "unobtainium" (really, Cameron? Really? That's the best you could come up with?) for themselves.
Also, because I hate blue monkey people that are supposedly more moral than humans. Said blue monkey people don't have the slightest concept of what mankind has faced, and overcome. They are in no position to judge.