Wow, that's really hard. The 2000s were the time when I gamed the most and some titles that stood out back then didn't hold up as well as I anticipated. Today, I'd argue the best games were also often the ones that changed the industry the most. Let's see...
- GTA III is definitely a contender. This was the game that really started the 3D sandbox trend and it's still a fun title today.
- Wii Sports Resort. I would've gone with the original but Resort was so much better. Wii Sports as a franchise signalled a huge shift in the gaming industry: Away from pure hardcore gaming into the mainstream activity gaming is today. Also, the game is just pure fun and to this day there's still no substitute for it on the Switch or any other recent Nintendo console or handheld.
- Resident Evil 4. What a monumental game and what a shift for the franchise. Resident Evil 4 is still one, if not the, best entry in the franchise. So much fun and it's such an arcade game at heart. As soon as there's a sale I'll buy it again for Switch so I can play it on the go.
- Bioshock. The atmosphere of this game was so amazing. I'm not much into FPS games but Bioshock really engrossed me in its world and mysteries.
- New Super Mario Bros. Wii. Today people think of this series as stale but this was only the second entry in the "New" series, the first home console 2D Mario since Mario World and the first time 4 player multiplayer was included. This game was amazing and we played it way too much in my group of friends. My best memory from the game is when we partied hard one night, woke up the next day and none of us could remember how we made it to World 7. So we just played through World 6 again lol.
- Metroid Prime. The gameplay is just addicting and the atmosphere great. Not sure what I can say about this game, it's just outstanding.
I really couldn't pick any one of these, though. The "console of the 2000's" was the Wii for me, so I'm naturally leaning towards Wii Sports and Mario. But picking one over the others is just too hard. Funny enough, my game of the 90s would be Ocarina of Time (followed by Mario Bros. 3 and Pokémon probably) and my game of the 2010's is Breath of the Wild but there's no Zelda in the list above.
Other contenders would be God of War 3, Pikmin, Oblivion, Mario Galaxy, Uncharted 2 and Twilight Princess but they just didn't quite grab me enough to be part of the list. I'm sure there is a bunch of games I simply failed to think of right now.
Would love to see one of these threads for the 90s and 80s, if these don't exist yet!