At time of writing, that award goes to Deus Ex: Human Revolution in my book, narrowly beating out Batman: Arkham City.
Of course I'm still waiting for the new Assassin's Creed, but as good as I think it will be, in the end it'll just be a polished version of AC2, meaning more of the same. Good, yes, but nothing I haven't seen before. That's why I pick DX:HR - on top of it being a great game, it was something I hadn't really played before, ever. (And don't you waggle your fingers at me, nostalgia buffs - I didn't play DX1 back in the day, so my point is not invalid.)
As for anyone possibly blaring 'Skyrim' in my direction... I'm not a huge fantasy fan anyway, and even though I'm resolved to play it, I'll wait until spring next year, so Bethesda will have had enough time to patch the five bajillion bugs their games typically suffer from at launch.