OpenXcom? I think games that are repetitively fun and where you build up your forces is always amazing. To some extent, a lot of turn based strategy are like that. What about fallout 2 and the baldurs gate series?
-Doom 2 - I'm SURE I played more than 5,000 hours of Doom 2 already. Ever since the game was released, I always play it from time to time. Nowdays, I mostly play Brutal Doom with random generated levels. ^^
-Skyrim - Even though its my least favorite TES, I've clocked more than 400 hours in it. MODs REALLY extend the life of those games. ^^
-Transports Tycoon Deluxe (actually OpenTTD) - One of the best games ever made. I think I have something like 2,000 hours, since it was released. A timeless classic. ^^
Difference between 30 and 60 FPS. If you can't notice it, you need new eyes. http://30vs60fps.com/