I’m going to cheat here a bit, so feel free to disqualify my picks, but both of the games I’m listing had DS sequels that didn’t even do the same thing as the original games.
Elebits- this game was fantastic. One of the best uses of the Wii pointer and its motion controls. A top 10 Wii title for me, in spite of it having one of the cringiest stories/voice acting I’ve ever heard.
Chibi Robo- I feel like this game is the answer to so many questions. Most underused IP? Chibi Robo. Game that never got a fair chance? Chibi Robo. Game that never got a “proper” sequel, Chibi Robo. The gameplay loop is No in line with today’s cozy games and I could even see it having some sort of “you ran out of power but were revived” roguelite version. It’s a shame this came out on the fading GameCube. I wonder if it would have had a better chance on the Wii, but they probably would have tried to shoehorn in some wiimote gimmicks so it’s probably best it wasn’t. Either way, this game has Dreamcast energy: a game that those who played it loved, but yay never really got the chance to sell.