Very tough match-up and I would never say anything bad about the greatness that is Wario Land Shake It.
I will, however, advocate for DQ IX. It is a fantastic RPG that is so refined, it does away with pretty much everything that can sometimes make RPGs tedious, yet it is still a long and engaging game. The story is great, the visuals are fantastic, the music is lovely, the game world is huge and the environments varied and interesting. The combat is straight-up turn based but there are lots of jobs, items, weapons, abilities and spells to explore and utilize so the combat is rarely boring. Plus, there are no random encounters. You can avoid as many battles as you wish. A first for the DQ series.
Add the fact that this game featured Street Pass before there was Street Pass (this is a DS game) and some excellent local multi-player mechanics, and you have a truly great game.