PC exclusives like rts titles, the witcher, crysis, etc aren't appealing to me in comparison to the exclusives found on the 3 main consoles (mario, gears of war, ninja gaiden, uncharted, etc).
Pc gaming is expensive regardless of how you do it, one gpu upgrade can set you back the price of an xbox, yet the performance boost you get from that rarely seems to actually matter as developers don't even seem to take advantage of the full brunt of PC power these days, you get a rarity like crysis or the witcher 2 that occurs every couple years, but devs don't seem to cap out pc capabilities imo.
Complexity in setup, anytime i've ever played pc games spanning all the way from the dos era to current windows 7 64 bit, I have always encountered some kind of issue with a batch of games, bugs, issues modding the games (a perk to pc gaming), driver compatibility issues, etc. While I have the capability to remedy those types of issues either on my own or via a google search, I find in my adult era (I used to pc game more as a kid) I just feel the time wasted doing those things is better spent elsewhere. Consoles you hit the button and go.
Local multiplayer/comfy couch syndrome, oddly I don't use the couch for gaming most, but the point stands somewhat, I as of now have 4 dedicated game boxes under my tv, as well as one laptop that powers my 20 inch pc screen, hooking up my laptop to the tv would not yield even 1/3 the result of graphical abilities my ps3/360 can do, yet it does everything else just perfectly, going out to buy a dedicated HTPC or something just so i can play batman arkham asylum with higher resolution and better textures just doesn't seem like a good idea at this point, when new batches of consoles are on the way that will surpass whatever is out now for awhile. With that said, it's also much easier to have multiplayer sessions with a console, you can either hook up 4 gamepads to a pc (why?) or just use the ones you have for the console already hooked up to the biggest tv in the house. Good luck playing kinect sports, gears of war or mario kart cafe on the pc, you know?
In general, it comes down to exclusives, cost and ease, the pc seems to get rare exclusives on occasion, but when it does it's not even my type of game. Meanwhile a flow of marios, halos, gears of wars, crackdowns and uncharteds keep coming on the consoles which do suit my taste do.