Get a DS then. If you ever played Maple Story, guess what? It's going to be made for the DS!

http://gonintendo.com/?p=2591

It's a pretty good PC MMORPG despite it's 2D graphics. The DS version should be better, and provide a good RPG experience on a handheld. I'd check out the PC Version before buying the DS ver. once it comes out. The PC version should give you a general idea of how the game will be like.