Anything Mega Man & Castlevania*, particularly looking forward to the SNES ones since they just never ran well on any other handheld I've had. Same thing with Super Mario World.
A bunch of vertical shooters would be sweet too.
* Sidenote: A YouTube video showing Mega Man X and/or Super...
Sorry about stuttering, repeating and general English fail (it's "disconcerTing"...); still think Cartoon Network and computer games did a decent job teaching me.
Can't wait until they're easy to buy (and/or more importantly; I have the cash ready)! It's like it was made just for me.