Retro for me are the NES, SNES, Gameboy, etc. Stuff that was either only in black and white (Gameboyyyyy, first one anyway) or could only be 8-bit or akin to it.
Classic for me, is something that I think I will always love, no matter how old it gets. Halo is a classic for me, as well as Sly Cooper, Morrowind, COD4, The Windwaker, RE4, etc, etc (I started gaming on the Gamecube for consoles, and Gameboy for handhelds, so I totally skipped the N64, Dreamcast, PS2... a lot of my "classics" are not that old).
So I guess for the purpose of the thread, I think the SNES, NES, and Gameboy are retro. I don't think any console is a classic, only the games on it that you will always play.