Gears of War 3 to me is the one I'm much more excited for. I LOVED Uncharted 1 and 2 but probably not as much as it seems many did. Uncharted 2 is easily one of the better games of this gen but to me Gears of War is the best new IP of the generation so far.
I'll be getting both day 1 but Gears just has the PERFECT gunplay for a TPS and will have an incredible extensive online component. Plus Gears of War campaign Co-Op with a buddy is the best co-op experience of any game on any console.
That being said I can already predict Uncharted 3 will easily win this pole. Sony fans dominate the site so hopefull we can get some good discussion going on in here but given past threads on similar things I wouldn't be too optimistic.