I was saying this in B8C yesterday but honestly, for me, SSBB/FFX/RE4/SSBM would all have been good winners.
RE4 is one of the most ubiquitously popular games out there. The amount of people who actively dislike it, from my experience, is very very small. Good sales, critically well-received, completely revolutionized a series and genre, has a cult fanbase and mainstream success.
SSBB and SSBM are both great games in their own right and the tournament fell in a way that had them set to meet each other.
Honestly they were both well-received, both well-liked, both had fantastic selling points. They both delivered in pretty much every way, and whichever one won would have been a fine winner.
I personally loathe FFX but it's a good choice if we're calling something GotD. On a site that loves jRPGs and Final Fantasy in particular, you have FFX, which is pretty much indisputably the best FF (and arguably jRPG) of the decade. An incredibly well-received game and very loved.
The only criticism of it is that, because of how early in the decade it came out, it could be seen as a shadow of the 90s in the way MM is. But I think being a PS2 game - undoubtedly the console of the 00s - kind of puts that one to bed. Plus it came out well over a year after MM.
MM was a horrible winner, the definitive example of people just flocking to "The Zelda Option". Developed in the 90s on a 90s console with a 90s engine, the inferior to OoT in terms of criticism and fan reaction. Just terrible. GSC would have been a poor winner in a similar kind of way, so it's not some kind of anti-Zelda or MM bias (I've never played it).
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