We know who rigged it! Congrats Blizzard! Congrats Jeff Kaplan! <3 OW.
The very sad reality is despite the populace shifting more towards multiplayer games for years, awards do not reflect that. I honestly believe that's because of two reasons. One because games media does not play multiplayer games for a long period of time due to the nature of their work. And two because if you don't put in the effort to "git gud" you'll lose which can lead to frustration and you won't experience the higher level of play multiplayer games have to offer.
Looking at the history of Spike's Video Game Awards it's clear that games media is unlikely to EVER give a game Game of the Year due primarily to its multiplayer component.
Before I list these off I want to make it overwhelmingly clear that I love a lot of these winners and some of them absolutely deserve the win.
In 2004 GTA San Andreas won over Halo 2.
In 2005 Resident Evil 4 won over World of Warcraft.
In 2006 The Elder Scrolls 4: Oblivion won over Gears of War.
In 2007 Bioshock won over COD4 (which wasn't even nominated) and Halo 3.In 2009 and 2010 Uncharted 2 and Red Dead Redemption won over both COD titles, both Halo games, Left 4 Dead games etc. You get the idea.And Mass Effect. Nothing to do with MP I just had to note that.
Fast forward to 2014 to the first annual Game Awards. Dragon Age Inquisition (jesus christ) wins over Destiny and Super Smash Brothers Wii U. That was just a bad year for gaming.
This year 2 multiplayer games are in the Game of the Year nominees. Overwatch and Titanfall 2. Titanfall 2 was lauded for its single player campaign so it got nominated while Battlefield 1 which is being lauded for its multiplayer didn't make the cut. Other than Hearthstone Overwatch is the only multiplayer only game nominated in over a decade.
So yeah it seems like unless games media pivots hard from a decades worth of history Overwatch won't win game of the year regardless of quality. I hope they do though.