I can't handle much multiplayer gaming, apart from COD 4, ET: QW, FEAR and SOF2 back in the day. Other games such as CS:S, TF2, etc, etc are good for short bursts, but generally I feel like I am just wasting time when I play multiplayer.
I just get a lot more satisfaction from completing a single player game. Though even with SP, in the past I used to have problems finishing games. Especially on PC - on the 360 I find it a lot easier playing through a whole game.
I guess its just easier to relax in a single player game (even the action games) whereas with MP you constantly got to be moving around and on your toes. It's why I love Crysis - nice open environments with enemies spread out so I am not constantly having to kill stuff and can take time to appreciate the scenery