Fantasy Zone 2 might be the most beautiful 8-bit game ever. It's also really, really fun.
Dragon Crystal is a pretty hard roguelike, but I really like all about it. Give it some tries if you can (it'll take some time to understand it).
I was doing fine with Dragon Crystal on Game Gear (3DS version) till I ran into a big eye or something that insta killed me. I was like what the hell do I do to beat that enemy or do I run away.
When looking up what that game was earlier today, I was looking a LP, explaining some of the ins and outs of it.
Too bad I don't have my SMS anymore (broke in an accident), otherwise I'd check if I could find it, there's a computing Bazar once a month in town with everything around PC and consoles, so chances are I'd find it there someday.
The Nintendo eShop rating Thread: http://gamrconnect.vgchartz.com/thread.php?id=237454