I've not stayed at many that I can remember, but in recent years, conventions have always been involved.
So...
- The Gaylord National Harbor(National Harbor, MD): the place is XBOX HUEG, and the atrium is amazing. Although the Residence Inn across the road narrowly edges it out because, hey -- microwaves and free breakfast.
- The Holiday Inn Inner Harbor(Baltimore, MD): my home base for Otakon. Rooms in the main building are good-sized(I wouldn't recommend stuffing rooms in the second building), plus microwaves and fridges. Plus everything important is at most two blocks away.
- Embassy Suites Hampton Roads(Hampton, VA): while I prefer the Days Inn close by due to it being cheaper, the Embassy is amazing. rooms are HUEG(plus microwave and fridge), plus an incredible free breakfast. Oh, and free booze. Granted, it's one drink per person per night, but still -- hey, free booze!