Viewtiful Joe: Double Trouble! was the first portable game in the series released in 2005. While I loved the first game in the series, I didn't get this sequel.
Which is pretty strange, since the graphics are pretty good for the DS. The game-play is kept mostly the same, with one screen showing a magnified view of the events going on in the other. There was also some touch-screen elements.
I think the biggest reason why I didn't get it was the mixed reaction from critics. Some loved it while others weren't so impressed. I eventually bought other games for my DS, and Double Trouble was long forgotten. I might give it a try if I come across it again.