>>189
It depends. Game-Boy Colour, N64, Neo-Geo Pocket Color, Wonderswan, N-Gage, Pokemon Mini, GP32, Tapwave Zodiac, Game-Boy Advance, and DS were all ROM based. (Plus JP SNES wasn't discontinued until 2003, for example.)

PS1, Dreamcast, PS2, Gamecube, Wii and PSP would all be ISOs. (Xbox/PS3/360 aren't yet able to be emulated reliably so they don't count.)

Also: obligatory mention of PowerPC Macs (good) and Windows Vista (not so good.)