I just started a game of Phantasy Star for the sega master system. It's a nice slow RPG that's well suited to the tiny d-pad. I loved it when I was a kid, but never finished it. It's still fun. Only problem is that my save got lost somehow after about 4 hours. I don't get that.

The best game in human history is Super Metroid for the snes, but it's way too fast for the small d-pad, and remapping the buttons would be very confusing. I'm not even going to try.

My list of games to try on the n810:
Pacman2 SNES
Zelda oracle of ages -GB color
Zelda oracle of seasons -GB color
I may try metal gear for the NES that seems slow enough
I'll also try Wario World2 for GBC, but I bet that's too fast too.