Well, there's Morrowind for sure. I've got this weird gap in my memory about a month large where I can't really remember anything except that I played Morrowind. A lot.
This also happens whenever I finally get to play a game that I have been anticipating, like, FOREVER. For example, I recently got a working PSX emulator which was extremely exciting because I've always been a ridiculously loyal Nintendo fanboy, and have therefore missed out on a ton of good games for the PlayStations. So I've recently been spending every waking hour catching up on the classics. Symphony of the Night, Final Fantasy 7-9, Xenogears, the list goes on.