1. Arcade
2. Sega Dreamcast
3. . . . whatever everybody else prefers, really.

1. SNES
That's it. It was the last of the old consoles that I had before moving on to PC-gaming for decade+ until I got a PS3.

1) Amiga
2) Commodore 64
3) Arcade
Seems pretttty dang obvious to me. Every other platform listed as a possibility is already well served by ports, remakes and official emulation. The Amiga and C64 had a lot of tremendously interesting games that folks outside of Europe don't generally seem to know about.

1.Megadrive
2.Snes
3.Arcade

1. Sega Dreamcast
2. Super Nintendo
3. Amiga

1) Amiga
2) Dreamcast
3) Arcade/coin-op
Reason for #1 were that there were soooo many good games for the Amiga in the late 80s that need to be resurrected.

1. Sega Dreamcast
2. Sega Genesis
3. Amiga

1. Sega Genesis - (would like to see "Shining in the Darkness")
2. NES - not listed but too many classics to not vote for it.
3. Super Nintendo

1. Amiga
2. Dreamcast
3. C64

1- Arcade (WonderBoy in Monsterland)
2- Amiga

Hmmm... I'd have to go with something like:
1. Dreamcast
2. Neo Geo
3. Mega Drive
...but really I'd want them all, given the choice. ;)
One thing I would hope is that these games would be released at a new, lower price point or bundled as a whole series in one package or something, because there aren't many console games I could see myself paying $5.99 each for.
Also it goes without saying that the ROMs/ISOs should be directly accessible so I can use whatever emulator I want, whether that be in the install directory or as a separate download. I'm very picky when it comes to emulation, and even if your supplied emulators are really great I still wouldn't buy console games from GOG at all if I couldn't access the original game files in some manner.

1- Arcade
2- Super Nintendo/Super Nes

c64
Atari 800
Sega Master System (SMS) :)

Before making stuff for another platform than PC, I think it would be great to make stuff for Linux and Mac OS.

1: Amiga
Many Amiga games have superior releases compared to their IBM PC DOS counterparts. While the graphics gap closed up with VGA, the sound gap was still pretty wide. There are also Amiga games that never got PC releases to begin with.
2: Arcade
This is a really broad category, which would also include the Neo-Geo (the MVS and AES are practically the same underlying hardware). I still choose it because many arcade ports end up losing something because the home hardware at the time had nothing on arcade hardware.
3: Sega Saturn
You read that right. Not Genesis/Mega Drive, not Dreamcast. Saturn. Yes, I know it's very difficult to emulate, what with all the processors and timing sensitivity, but many of its best games have ludicrous prices that keep people from being able to try them out. Guardian Heroes, Panzer Dragoon Saga, Radiant Silvergun-you know all too well what I mean. The other challenge, though, would be translating many of its best releases into English, seeing as practically half or more of the Saturn's best games are Japan-only releases.