The Lost Boys is a classic.

I haven't seen any other of his movies yet but The Lost Boys was awesome!

Um...not to be rude or anything but you do realize this pick doesn't conclude his entire list of appearances, right? Silver Bullet, Last Resort, Murphy's Romance anyone? I'm assuming these weren't added to the pick as they are less known...I'll just do an updated pick, it's fine.
Lost Boys will forever be a classic but it's kind of obvious that it will win. Blown Away is alright, not that great though. Watchers & License to Drive are tied for me but Lucas will always be one of my favourites. :)
Oh yeah sorry if I sounded like a bitch before but I just like to get my facts right. :|