I am going to through some Luigi's Mansion love out there too. I loved this game when it came out and I felt it was the closest I would ever get to having a Ghostbusters game, luckily that changed.
Also Zelda Four Swords Adventure was amazing and I only discovered it last year cause I thought like the GBA game you needed 4 people to play. Four Swords on Gamecube was like playing the Link to the Past sequel I always dreamed of.
Mario Sunshine is one of those games I was in denial about not liking. While the first play through was ok, it just did not have that "wow Mario a new Mario game!" feel to it. Like the system this is one of my least replayed Mario games.
i actually think it's better than galaxy, since there's less moments that give you frustration (with the rope walking as an exception) it's one of those games that i let go in playing for a while then come back to. truth to be told though the beta looked a lot better. it ran in 60 fps, unlike the final game in which the fps was cut down to 30