As far as BEST movie goes, I don't think I've ever seen a better all around movie than Titanic. Love story or not, that flick had it all. GREAT movie.
As far as my favorites go...in no particular order (but the GREATS are bolded):
Ferris Bueller's Day Off
Clerks
Mallrats
Jay and Silent Bob Strike Back
5 of the 6 Star Wars movies
40YOV
Superbad
Knocked Up
Forgetting Sarah Marshall
Dirty Rotten Scoundrels
Lost Boys
Tombstone
Waiting
Grandma's Boy
Walk Hard...Dewey Cox Story
Transformers
Empire Records
Happy Gilmore
Billy Madison
The Girl Next Door
Harold and Kumar go to White Castle
The Crow
Dark Knight
I'm sure there are more. I'll post as I remember