Hmmm, I've watched a lot of movies over the years. Don't know if it's possible for me to pick a favorite. I'll list some of the more exceptional ones, old and new.
The African Queen
Mister Roberts (The original one)
Heaven Knows Mr. Allison
The Longest Day
Cool Hand Luke
Deliverance
The Shawshank Redemption
Empire Of The Sun
The Aviator
Running Scared
Shutter Island
Michael Collins
The Wind That Shakes the Barley
The Boondock Saints
The Departed
Good Will Hunting
Inception
There's just too many to remember.