I will take this as a personal affront! (not really)
It's something I've thought about quite a bit and wonder if there really is a solution... Older games get updated a lot, and a lot of work goes into those updates, yet by virtue of the base game not being released in the year the major update was, it stands no chance of winning an award.
Now The Witcher 3 is a bit of an extreme case because it won a GOTY award last year, so it's a bit rough that it was in the running *again* this year because it released an expansion.
And yet despite that, the tribe has spoken, and I completely get why - it's an excellently crafted story over 20 hours of new gameplay (on average). It *is* a whole new game, you just happen to need the previous game to play it.
Let's take another game like No Man's Sky. Hello Games can roll out a patch next year that makes it the greatest indie game of the decade and unless it rolls it into a new game and charges for it, it can't be nominated for an award?
That's why I nominated Diablo 3 this year. No-one would vote for it, but I feel it deserves at least a nomination. They added a solid amount of content over the year, changed up the metagame, and manage to keep a significant community going around a non-tournament game. All for free.
(Similarly, Broforce probably won best SA-developed game despite being "released" long ago, and it was nominated by virtue of being released on PS4 this year.)






