I'd recommend Mario Kart DS which is my favorite mario kart ever and has incredible replayability, seriously hundreds of hours.
New super mario is pretty good too and even includes a few minigames which are fun with another player.
Advance Wars is repetitive but surprisingly entertaining and very addictive.
As for the Brain games, not everyone likes them, I think they are pretty fun actually and a change from the usual games.
I would not recommend getting FFIII : I was pretty excited about it but it turned out to be quite a disapointment. Story is extremely lame and basic, the fighting is just terrible (yes there are different "jobs" but once you've selected them for your characters, you always do the exact same attack with each one of them a thousand times.
Sonic Rush was quite disapointing also, but I was never a huge sonic fan.
I've never played Kirby Canvas Curse, is it really that good and do the controls work well?
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