Movies
When Lord of the Rings came out, I couldn't watch it enough times. It felt revolutionary to me (maybe because I had gotten too busy to watch many movies). Now I kind of can't stand it, except maybe for Liv Tyler who reminds me of a girl I once knew.
The Batman trilogy. At a young age, I read a lot of comics and Superman was by far my favorite. Batman just didn't have the right value proposition for me. But when I watched the first Nolan movie, I was blown away and it was a movie I went back to watch several times. I will watch it still now and again. Amongst an amazing cast, Heath Ledger was mind blowing.
TV Series
Breaking Bad. After the first time, I haven't ever watched this right from the beginning, opting instead to start from a later season. I told myself that I shouldn't spend all that time watching it again. But recently I went back to watch it from season 2 and realized I had missed out by not watching the build up to the later seasons.
There may be a few other movies I have gone back to watch again eg Godfather, but generally I don't go back to watch something I've already seen, including many excellent movies. The above are what I have probably watched "too many times".
What about you?