I tend to play a lot of sandbox-open world type games or just games with a lot of options that requires me to sink tons of hours into exploring every facet of that world. A couple examples of this are The Elder Scrolls series (obviously), sometimes Dragon Age, Mass Effect, other CRPGs, Planescape Torment, Baldur's Gate and other D&D inspired stuff, MMOs in general especially WoW, GW2 and SWTOR with all their starting zones. It's usually the RPG type games with a lot of options that make me want to keep going, Minecraft too but that's not an RPG per se.
Single player shooters usually don't last long enough for me to really consider getting tired at any point, I usually don't play these games more than once anyways.
Although recently I've been a bit burnt out with Oblivion having basically reached the broken part of the levelling system twice, and completely almost all of the faction story lines (which are all really good and mostly better than Skyrim's). So right now I'm just boggled down in my D&D homebrew, actually that's a game that I never get tired of playing. Ever. DM side or as a player.