its impossible to port any official nintendo game on pc. Nintendo is keeping their TM very hard ... at least it was so far :)
anyway ...
1) Dreamcast (want to play Shenmue Ecco and Crazy Taxi)
2) it could be nice to play Game Boy (Color) games on official emulator on pc ...
3) Atari Jaguar

i hope nintendo permits it! i want to play my nintendo64 classics on pc...

1) Amiga
2) Sega Dreamcast
3) Commodore 64

1)Dreamcast
2)SNES
3)C64
I own all of these Systems, but there are games I never got my hands on.
And besides my discs and cassette-tapes DO age just like the GDROM of my Dreamcast.
I would love to see the JRPGs on the SNES and the beat em ups from the Dreamcast (PC doesn't seem to have that many good Beat em ups...if any).
And of course: I still want to get Shenmue 2 for a reasonable price.
And no, playing console games with the keayboard is probably not going to work well. But on the other hand: A sturdy Gamepad is not expensive and mine has been serving me for the last 5 years.
At last: I wouldn't be mad at GOG even if they reduced their PC-Game Output in favor of Consoles. Currently they release more games of interest to me than I can play (by far). And if they've run out of Publishers that let their PC Games be sold without Protection, then I'd rather see some good Console releases than bad/no PC Releases.
And just like with Question Round 1:
My biggest wish is for you to stay in business, so don't take too many risks ;-)
Greetings
Edit: Typos and word choice

1) Mega Drive (Genesis)
2) Nintendo 64
3) Torn between NES and SNES
1 Because of the legendary Sonic games, Desert Strike and Ecco the Dolphin
2 Purely for Super Mario 64, which I never got to play.
3 For all of them great, classical games

1. Nintendo 64 - Best console ever made
2. PS1 - Hundreds of games
3. Super Nintendo
Not a lot of people know Final Fantasy VII and Final Fantasy VIII were ported to the PC. If GOG could add those, I'd buy em.

1. PS2 - To have some of my favorite PS2 games playable on a laptop would just be incredible!
2. Nintendo 64
3. Commodore 64

Dreamcast of course, it's the hardest to emulate so if you included it that would put an emphasis on improving this.

1. Amiga
2. Dreamcast
3. Nintendo 64

Oh wow, interesting question. I would LOVE to be able to buy older console games too! I know there's Wii's VC, but it's DRM is *hideous*, and I'd probably rather have them for PC anyway.
Of the ones mentioned on the front page, my picks in order would be:
Super Nintendo
Genesis
Dreamcast
(There are a ton of Saturn games I'd love to buy or rebuy too, and a ton of NES stuff, so those would be on my list if they'd been in the GOG post.)
Personally I'm not a big fan of arcade games, though there are a small number I'd consider buying if from GOG.

1. Sega Genesis
2. Super Nintendo
3. Arcade
But any of the systems listed would be worthy additions to GOG.com

1. Dreamcast
2. nintendo 64
3. NeoGeo

Well all the others are perfectly emulatable except the Dreamcast.
So that would be
1. Dreamcast
2. Dreamcast
3. dreamcast

dreamcast
neogeo
arcade

If there is 8-bit C64 then where is Atari? :(