Sega Dreamcast
Nintendo 64

1. Sega Dreamcast
2. Games by Fumito Ueda, Ico and Shadow of the Colossus (prolly not happening).
3. Nintendo Gamecube

1. Sega Genesis + Sega CD(sega cd games are great, and relativeily unknown to alot of people, so these might sell because they are almost new)
2. Sega Dreamcast
3. Nintendo 64
4. Honorable mention NEC Supergrafx

Not sure if this would count as old but PS2 would be great. And I only say that because I despartely want to play Shadow of the Colossus. :P

My picks (in order of preference):
1. Nintendo 64
2. Super Nintendo
3. Sega Genesis

1. Sega Dreamcast
2. Arcade
3. Sega Genesis

Arcade
SNES
Megadrive
If you decide to do any of them, please try to make original Japan and Europe releases available. There are a lot of games that never came out in the States that I would love to try out.

1. Super Nintendo
2. Sega Genesis
3. Arcade

1. SNES
2. Genesis
3. Arcade

1.Sega Dreamcast
2.Super Nintendo
3.Nintendo 64
I already have a Wii, so I can do the SNES, and N64 games there, but I'd really like to see someone put Goldeneye 64, and Perfect Dark 64 into their library.
PS: Playing Sonic Adventure again would be a dream come true for me.

My vote goes to:
1) Dreamcast
2) Dreamcast
and
3) Dreamcast
Well, I didn't ever get to play on the dreamcast console, and I know it has a lot of good games for it.

1. SEGA Dreamcast
My absolute first choice. Just because some of the games for this platform are downright epic (personally I'm a great Shenmue fan).
If I have to pick two other consoles they would be:
2. SEGA Genesis
3. Super NES

1-Amiga
2-Arcade
3-Commodre 64

1. Sega Dreamcast - 'nuff said;
2. Sega Saturn - lotsa good games
3. Nintendo 64 - Goldeneye, Mario Party, Perfect Dark, Conker's Bad Fur Day, I could be all day long on this.

1) Arcade!
2) Atari, because as people have said, there are a lot of good games for it.
3) Super Nintendo.
As much as I'd love N64/Dreamcast stuff, I have no idea how that would actually *work*? It would be groundbreaking enough to get console games at all, but I was under the impression it was ridiculously hard to emulate them on a PC. Unless you'd be selling cartridges, which would be... strange...
And possibly net you guys boatloads of money, especially for those popular old SNES/Genesis games for which the current options are 1) eBay at five times original price and 2) "dropped off an internet truck"...
I can see the appeal. :3 Legal FF6, Earthbound, Chrono Trigger? Yes please. In my dreams, maybe.