I wouldn't bother with emulation on the DS. SNES was okay, Mario World works fine for me with occasional frame skips. I tried Mega Drive emulation but it just crashed on me.
From what I've seen everything 16bit and under, GBA and PS1 works like a charm. N64 is slow.
My fingers are sooo crossed for fast Amiga emulation. Turrican on the go would make everything complete.