My votes for 'best' on a lower-end system are: NESTopia, ZSNES, PJ64 (Beta version), MESS for Colecovision, Atari 2600 5200 and 7800, Intellevision and Vectrex, pSX for PSX, and DOSBox for DOS. Oh and VBA for Gameboy andv Advance, No$GBA w/ Zoomer for DS, and Fusion for Sega CD, Genesis, Master System, and GameGear. These have all been working great for me since the begining, and nothing could make me want to change. I might sub in MAMEPlus! for MAME just for the ability to filter the gfx too, but I use vanilla MAME since it's easier for me to compile my own build.