Animal Crossing is my number one GC game. It was also the first game I ever had for the console. If you like any of the newer Animal Crossing games you’ll 100% enjoy the OG GC one. It has a great art style to it that still looks good today, and I find the villagers are a lot more charming compared to the newer games. Downside is you’ll be missing a lot of the modern QoL features the modern games have.
There’s two Dragon Ball Z games I used to play the hell out of on GC, Budokai and Budokai 2. I still love both those games but I’m not sure how fun they’re going to be for folks who didn’t grow up playing them, as they have aged a fair bit.
The GameCube also has my personal favorite Mario Party and Mario Kart on it, those games being Mario Party 6 and Mario Kart Double Dash. For Double Dash, I will admit nostalgia plays a pretty big factor in why it’s my favorite, I do think Mario Kart 8 Deluxe is just a better overall game due to the variety. But Double Dash has a fun gimmick, and I think all the maps Double Dash has are quite good.
Need for Speed Underground 2, as well as Hot Pursuit 2 are both fantastic racing games from what I remember. I haven’t played them in a while so I’m unsure how well they hold up today, though the racing game genre as a whole is pretty rough these days so they can’t be that bad in comparison.
Battle for Bikini Bottom is an awesome SpongeBob game, but it’s also been remade for modern consoles so you might’ve played it already. It does have a sort of sequel game just called The SpongeBob SquarePants Movie, which is very similar gameplay wise. Little me never managed to actually complete it due to how difficult it was but I got to the second to last level at least.