I have many favourites that I rewatch when the mood strikes me, so I'll just share a few anecdotes.
I remember the first time Star Wars showed up on TV. The family of my friend that lived across the street were one of the first to get a VHS deck. Way back when they were top loaders. (They were East Indian and mostly used it for renting and watching Bollywood movies.) Anyway, I remember that my friend recorded the TV broadcast of it and we watched that quite a few times in the following few weeks.
When VHS movies first started getting released at "sell through" prices, the first movie I ever bought was The Road Warrior. I've watched that more times than I can remember. I eventually re-purchased it on Laser Disc and eventually on Blu Ray.
I also had Mad Max on both VHS and eventually the DVD that featured the original Australian dialogue track. I watched that old American International release of it so often though, that it's almost weird hearing the actual dialogue at times with the exception of Mel Gibson who finally sounds right.
Superman: The Movie -- when my VHS of it got eaten by my first VCR, I re-purchased it on Laser Disc. When the extended cut with all of the bonus features was eventually released on DVD, I picked that up as well. When I got my first PS3, there was a deal where you could send away for 5 free Blu Rays and it was on the list, so I picked that as one of my choices. I never had Beta... so other than that I've had a version of this movie on every other format available to date.
Star Trek II: The Wrath of Khan. I'm a fan of the entire series but I've probably watched that one more than any of the others.
A few other notable mentions for me:
Independence Day
Starship Troopers
The Adventures of Buckaroo Banzai
Any of the Dirty Harry series
Any Godzilla movie
Most John Carpenter movies but especially Escape From New York, The Thing and Big Trouble in Little China
Most Brian DePalma movies (Blow Out and Dressed to Kill being my favourites)
Rocketeer (Disney finally released it on Blu Ray last year. No bonus features but finally a decent quality video because the previous DVD release was terrible)
Sleepy Hollow
And of course, Evil Dead, Evil Dead II: Dead by Dawn and Army of Darkness!!!
And many of the ones previously mentioned in this thread. My all time favourite movie being Blade Runner, which I have watched many, many times over the years.
