Well, it was my first GenCon, so take this for what it's worth...
The Westin (where I stayed) seemed pretty ambivalent. They were getting a lot of 'official' spillover from the convention center, but they didn't seem to do anything out of the ordinary for the gamer crowd. Plus they had some other problems. It was very convenient, though -- it was a matter of a few minutes to go from my room to anywhere in the convention center. The amenties were lacking as well, although the bed *was* nice and comfortable.
The Hyatt seemed the most gamer friendly -- nice big tables set out for gamers, jugs of water and plastic cups to drink from, the Subway and McDonalds downstairs kept longer hours (or longer than I would have expected, anyway -- don't know what they normally do).
Embassy Suites seemed ok, and tolerant of extra-curricular activities. I was only there briefly for Canadiana and a game at Old One's suite, so I don't know if they did anything special. I don't think they had as much room as the Hyatt, so laying out lots of tables and such probably wouldn't happen.
Given one year's experience, I will probably try and stay at the Hyatt next year.