I have mobile emulators. The touch controls are so damn uncomfortable and it's hard to get them right. I used to play them on my old phone using a Wiimote as a controller, though, and that wasn't all that bad: I managed to play through the first four Battle Network games on this setup. Anything up to the GBA runs pretty smoothly on recent devices (I mean, they can even handle PSX emulators with ease).
RPGs are way more bearable to play, there. I played a bit of Fire Emblem and Golden Sun on mobile, and I didn't feel limited at all. I tried to play Chrono Trigger, too, but I switched to PC soon to enjoy it to the fullest.