re: emulators and roms

The 2 top SNES emulators are:

LINK

and

LINK

The second one (ZSNES) is considered the best, but I have seen a couple compatibility issues, one game being Super Mario RPG, there is a known issue where the game stops working when opening the equip screen sometimes.

The good thing is, if you save a game on one emulator, when you open it on the other, the game is still saved in the same spot.

What I would recommend for you, is that any game you want to play, just do a quick check through google and see if a game runs better on one emulator over the other. They are both great, so just install both.

Best NES emulator I've used: LINK

Best SEGA emulator I've seen, if you read the description, you'll see that it actually runs games from several sega systems, not just the genesis: LINK

As far as ROMs go, 2 options. You can google specific games with the word ROM behind them and just get them individually, or as the above poster stated, if you use torrents, I've gotten entire packages of games at one time from trusted sources on thepiratebay and other places.