But what you really want to do is just buy an old XBox, mod it, then put on ZSnexbox, NeoGenesis, HugoX, FCEUltraX, XBoyAdvance, MAMEoX, SMSPlusX, NeoPopX, DOSXbox, Surreal64, and finally FinalBurnXXX. Then you have a box that holds all your ROMs and savegames/savestates, plays them on TV like you're supposed to, and has 4 convenient joystick ports. You can easily make a USB attachment for mouse/keyboard (DOSBox, Mouse on Genesis/SNES, etc).

On the PC, I'd say the same:

> Genesis : Gens (Kega Fusion is also complete, but i am more confortable using
> Gens)
> Master System : Meka
> NES : NEstopia (seems to be good enough) and NesterDC (on the Dreamcast)
> SNES : ZSNES

But I also like DSMS (never tried Meka) because it's got a graphical filter that makes SMS games look like it's hooked up by a composite cable, and also you can pimp out the SMS sound by turning on General MIDI (if you never did this, you have to hear it). I also like FCEUltra because you can enable the 6th NES sound channel for some pretty sweet sound on a lot of Japanese games, plus it's meticulous in its emulation of the NES (too bad there aren't any PSX or N64 emulators that are this accurate).