1. Sega DreamCast
2. Arcade
3. NeoGeo

1. Commodore 64
2. Amiga
3. Arcade
I'm surprised Nintendo consoles are on that list, since I'd assume that's an impossibility what with Virtual Console's lockdown. I wouldn't think Nintendo would allow anyone else to distribute games on their past consoles.

Nintendo 64
Amiga
Dreamcast
In that order.
The Nintendo 64 has a ton of great games that could use some post console loving. Perfect Dark, Conkers Bad Fur Day, Ogre Battle 64, to name a few non Nintendo games.
The Amiga, tons of great games, that stand up to even most of today's games. Hired Guns in particular is one of my favorites, Myth and Wings, along with Cannon Fodder. While the C64 was my favorite system of all the listed ones, I find it difficult to believe many of those games would be something people would pay for especially with the many fan sites.
The Dreamcast, some claim died due to software piracy, a claim I disagree with. It was very hard to attract companies to the Dreamcast at that time. (I believe it was due to a lack of support by a few major publishers that shall remain blameless and nameless. 3 consoles with blown controller ports might have also have been an issue and thats just in my home. ;)) It should be noted that if the detractors are correct in this case, it would not help GOG and would hurt the bottom line. But, there are a ton of titles that are completely worth buying especially if you include imports. But, imports are a bit of a different market that I'm not entirely sure GOG would benefit from financially. Now, would it make me happy? Yes.
As a note: TheOneGuy
Just because Nintendo won't release their own games, doesn't stop independent companies from re-releasing it.

Sega Genesis
Commodore 64
Arcade

1. Amiga
2. Super Nintendo
3. Nintendo 64

Yeah, i second that. It's time now gog, begin offering made for linux and mac binaries already! Unless it's easier for them to bundle windows only console emulators with the console roms...

1) Super Nintendo
2) Sega Megadrive
3) Neo Geo
I choose these three machines because I thin they are the best choiches about the 2D graphics. I would pay attention to Dreamcast, because Sega should announce at that E3 that will be sold Dreamcast games with the PSN. Remastered in HD and with the trophy system!. Maybe you of GOG can ask them to do a similar thing with us! But an emulator for PC... It' ought be too heavy for my poor old PC...
I would even avoid N64. Except the fantastic Mario 64 eand the two Zelda (that I bought and finished with the Wii's Vrtual Console), it's game are in a old 3D. Shouldn't be very good on PC... In addiction, many lovers of retrogaming have some years, and probably N64 - as the fistr Playstation - is a machine too much known. It's not old enough!
2D. Forever young! And I would try Neo-Geo games, too much expensive fifteen years ago!
Thank you for your work!
P.S.: Excuse me for the sad english, I'm italian. I hope that you could understand my words.

1. Amiga
2. Amiga
3. Amiga
Huh? Oh, different ones? ok, then...
1. Amiga
2. Nintendo 64
3. Sega Megadrive

1. Nintendo 64
2. Super Nintendo
3. Arcade

1. Arcade
2. Amiga
3. SNES

1 - AMIGA
2 - C64
3 - ARCADE, Bombjack etc. !!
I suggest making classics packs for any of the above .. Maybe ask people on here about what games would be worth paying the authors for .. For that is really what all this would be about ... Getting some cash back to the authors of REALLY GOOOOD OOOLD GAMES !!! :-) And massaging the consciences of us super conscientious Amiga/C64 users who have tons and tons of downloaded stuff that we really would want to pay a little for, preferrably to the individuals behind the games instead of leeching yet again - like so many of us did back in the day ......
If you should decide to do anything with the Amiga / C64 stuff you should work with the guys behind AmigaForever and C64 Forever from Cloanto in Italy ... And maybe Magnussoft (I think that is some guys who have some Amiga / C64 compilations in Germany .. )

1. SNES
2. N64
3. Arcade

1. Super Nintendo
2. Nintendo 64
3. Sega Genesis

1 Amiga
2 C-64

1. Dreamcast (I totally missed this console and it's rare, but amazing sounding games and would love the chance to experience any of them.)
2. N64 (Ditto.)
3. SNES (I grew up on this console; everyone needs to experience the nearly unheard of Uniracers. Period.)