I mostly agree with you joshsquall. Most movies are a massive waste of time the first viewing, and the second viewing is just painful. I'll never buy a movie for that reason. However, there are a small handful of movies that I will rewatch.
I'll watch either Rudolph the Red Nosed Reindeer or A Cristmas Story around Christmas time. Sure, I know the plots and the jokes, etc. But it just puts me in the holiday spirit to watch one.
I watched Monty Pythons The Holy Grail again last night. It had been several years so I forgot many jokes, and laughed again. Heck, I was laughing so hard just putting in the DVD as I thought about the rabbit scene. My GF thought I was crazy laughing before the movie. Also, she had never seen it, so it is great to cuddle up and I can pay more attention to her while a movie is going on.
Like others have said above, sometimes you'll miss something the first time through. You need to watch Airplane at least a half dozen times to catch all the jokes in the background. I didn't understand the Mayo Clinic joke the first time when I was young (they call a clinic and there are jars of Mayo all over, but I didn't realize that a Mayo Clinic was a real thing back when I was a kid).