Undertale - Melee, so good it'll make you betray Undertale!

Only one place to settle this

The whole concept of "Best Game Ever" (and to some extent, GOTY) is moronic to begin with. Gaming has too much to offer to feature everything interesting it got in a single game.

The only reason this term is so popular nowadays is because it's the cheapest tactic to launch polls and threads to stimulate a community. And I'm convinced it's rather recent (10 years ago, I saw few to no threads discussing this), because of the rise of social networks and message boards to some extent. Plus, this kind of poll is biased by definition because you would need to have everyone having played every listed game to have a seemingly credible result (otherwise, it's impossible for great games that didn't sell well like Okami to stand a chance).

IMO, attempts at listing "great" games (because they are original, rich in terms of gameplay, smart in terms of level design, have a great storytelling, etc.) are much better than trying to pick up the "best" one (plus, what are the criteria to be the "best" vidya ?).