It depends on the game. I enjoyed Borderlands, so buying Borderlands 2 and getting Gaige was a no-brainer.
For the new XCom game, I had been following it and seeing that it was fairly similar to the original with modernization. Preordered. No regrets. I still play the original, and this is a good recreation.
Impire, in the vein of Dungeon Keeper, no regrets. Demon rebuilds power and takes over. I like being the bad person! :D Loved DK1 and 2! :D
Brutal Legend, yes, I wanted this game since it was announced for consoles. DoubleFine Studios with Jack Black, SOLD!
The Cave, yes, DoubleFine! :)
Ys 1 and 2, yes, loved the originals.
The rest of my games tend to be from Humble Bundles sales, Steam sales, or GamersGate sales on Steam games. :)
I have also Kickstarted quite a few games. Strikesuit Zero is one of them.