I've been having a blast with Devil May Cry 4 of course I've only bought 4 PC games this year (Sins of Solar Empire, Mass Effect, GRID and DMC4) but it's definitely the best of the bunch, GRID is also great, Mass Effect had too many crashes for me and when I finally fixed them (by installing the game on Vista) I was already disenchanted with the game (it's too repetitive) so I'll come back to it later, Sins was excellent but it got boring fast, I hope they release an expansion with a single-player campaign soon.
I wouldn't say any of them are GOTY though, I'm eagerly anticipating Spore, Crysis Warhead and Pure in September though.