Guild Wars 2 deserves it. It's a really good game. Honestly the negative forum buzz reminds me of WoW and LoL for the first year or so of their release. Man, I remember WoW being bashed SO hard when it launched, and for like the next year after it launched. "This game is so bad compared to EQ!" "This game might be decent if the servers weren't always down!" "Blizzard should have stuck with RTS or made Diablo 3." Despite how the game apparently had failed in the eyes of forum-goers, it became one of the most popular MMOs of all time. LoL was very much the same way, though people were (and still are to a much lesser extent) complaining about how casual and watered down it is compared to DOTA...yet now, LoL is the most played game in the world.
I'm not saying GW2 is going to be, or is currently, the "next big thing." I just think the negative forum buzz isn't all that uncommon for these legitimately good games at launch. The people who didn't like the game will eventually move on. As long as ArenaNet does a good job supporting GW2, it'll continue to grow in popularity. Really nice to see it get all of these GotY awards.