For me it's a tie between Harry Potter and the Deathly Hallows parts 1 and 2, having watched them 27 times each.
There are many movies mentioned here that we have watched a lot, but as for those we watch annually, it would be Chevy Chase' Christmas Vacation and Groundhog Day with Bill Murray.
By far, my favorite movie of all time (and the one I've seen most) is Raiders of the Lost Ark. It's the first real movie memory I have (age 3?) and I've been Indiana Jones obsessed, seriously, ever since. I've also watched Rocky, Jaws, The Sound of Music, and The Ten Commandments (1st night of Passover tradition, plus a couple more times throughout the year) more times than I can count. And I'll own up to the fact that my hubby got me sucked into the Marvel franchise. I just can't help but enjoy them!
Last night, my girlfriend fell asleep on the couch next to me and I began channel surfing. I found Road House. It was the at the scene where the blonde does her strip tease and then the bar fight breaks out. "What are you watching?" she asked with her eyes barely open. "Go back to sleep, babe. Go back to sleep."