The only movies I have never tired of at all even after dozens of viewings are The Karate Kid, Star Trek II, and The Empire Strikes Back. I watched them so many times when I was a kid that now I consciously ration them out to make sure that I never get tired of them.
Next up with just a touch of hesitation are The Matrix (I think mostly due to the irritating DVD menu), Heat (mostly due to the length), Princess Mononoke (unnecessarily gruesome), Master and Commander (achingly slow part in the middle), Star Trek 4 (I never want to start watching it, but love it once it's on) and the LOTR movies (due to the foolish changes to add unnecessary whining and drama).
The only TV series I've devoured as quickly as I could get my hands on them (since the introduction of putting entire series on DVDs) are Nurse Jackie and Daria. Next up are The Simpsons and Battlestar Galactica (new one).