Most of the games that I play for a long time are games that don't necessarily have an end, and by the time that I am all done with it I'm simply ready to move on to the next big adventure.
As for games that I finish that have a clear cut end, I tend to either move towards that backlog of games I've intended to play but didn't or simply get an indie that looks interesting or go for something I wouldn't normally pick up.
Can't believe how much fun Rayman Origins was after Gravity Rush.
Here's my current order of gameplay: Zombie game, Space Sci-fi game and then Adventure game. I don't play online (have not since Feb 2011 but may in the future).
This is like Resident Evil/Walking Dead then Dead Space/Bioshock then Uncharted/Tomb Raider. Currently stuck on RE5 (just can't seem to play it). This keeps things pretty fresh for me. Maybe a good tower defense game or something different in there once in a while.
60GB Fat OFW 4.50
250GB SuperSlim OFW 4.50