Many favorite games, but longest played games for me are the following:
World of Warcraft ... been playing since beta, but due to some gaps in subscription I didn't get the 10 year gift from blizzard
Diablo II - Still play it on occasion when taking a break from wow. I got the free Diablo III for promo from blizzard, but prefer Diablo II instead of III
Torchlight - Best offline dungeon crawler when travelling and need to pass the time in airports or 35,000ft. However now that I got Torchlight II through Humble Bundle DRM Free I can now play Torchlight II offline while on the road now, so that game will be passing Torchlight 1 at some point in hours played.
Diablo 1 - Still enjoy it occasionally ... and I did click on the cow enough times to trigger easter egg in game...LOL
StarCraft - Use to play this for hours and hours, but kind of burnt out on it now. Same old grind for getting mats and building up to beat the computer AI etc. Fun is lost when using ShowMeTheMoney cheat.
Recent gaming:
Hearthstone - I have a friend who is helping me with knowing what cards to have in deck and how to play them out which has a certain level of complexity to it to not rush and sit on specific cards and take some damage to then use combinations of cards used to hit harder at opponent. Only concern I have with game is that it may be Pay to Win since blizzard sells the better cards, however I have been told that you can earn gold playing to buy them.