Depends of what games you like.
Super Paper Mario is a light, easy RPG that's quite easy to get into, play and beat. If you like easier games or RPG's in general, get that one first.
Metroid Prime 3 is the best FPS-type game on the Wii at the moment, period. If for some reason you don't like SPM (what's wrong with you? :P) or if you prefer shooters , buy MP3.
I'm assuming that Dragon Quest = Dragon Quest: Swords, which isn't apparently that great. I'd buy the other two games before even considering DQ.
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