I think what GW2 did to the stale MMO genre itself makes it deserve GOTY.
While GW2 is a pretty good game and personally, I thought it would shake up the MMO world for good. After 500 hours of play time, I'm quite disappointed, on many points its not all that different from
'Generic MMO #230'. In many ways it actually takes a serious step back, it also has some very glaring issues that caused me to stop playing and made me lose interest for future content.
Endgame aside from sPvP or dungeons is nothing but zergs, with tons of culling issues; WvW zergs, Plinx zergs, karka-event-zergs, etc.
Low-/mid level zones are completely abandoned, just like any other MMO.
Getting a dungeon party together is a flashback to 1999, where we have to stand idle in a big city, spamming chat.
Getting high-tier gear (dungeon-gear, named exotics, ascended, legendaries) is an (expensive) grind; much worse, and much more boring then traditional MMO's.
Very limited character (role) customization once you've taken a closer look at its mechanics.
Ingame performance is very underwhelming at times, e.g., Lions Arch or near zergs.
So, in my book: Good value for money, certainly. GOTY or exceptional MMO, no, not really.
More ontopic, I honestly don't know what game deserves my 'GOTY' stamp. Games I was looking forward to where GW2, TL2, BL2 and Planetside 2. Those are good games, but all of them have their flaws.
I guess for me, the closest to GOTY would be Max Payne 3. It really surprised me. Solid gameplay, interesting story/storytelling and great graphics. This might've been due to low expectations, trailers really made it seem like they butchered the franchise by skipping the whole 'film noir' Max Payne atmosphere, but I enjoy playing through it and left behind a great impression.