The sheer number of shooters may not compare but the quality is high. Same for 'sandbox' whatever that is exactly. I'm not sure of the difference between an action or western RPG in a sandbox setting and RDR or AC2 with all their rpg elements. I recognize AC as different from a Fallout but RDR is somewhere in between just as ME2 falls between RPG and TPS. Clarify my confusion if you can. Sorry, an idea for another thread maybe.
On topic I will say that imho and as a 360 only gamer no year has come close to 2010 in the number of quality titles in the genres I enjoy. There are another half-dozen great games still to come. There will be more legitimate contenders for 2010 GOTY than in recent years. I can't comment on the quality of arcade and other downloadable titles but xbl and psn are quickly growing in volume, there was a lot of very good add-on dlc this year and again, there's more to come. It's early but from the lists above, next year's line-up has only a few titles that I consider as must-own.
