It's pretty much been estlablished that the Revolution will have all the guts needed to play GameCube games. And Existing GameCube games already have mostly flawless emulation software for the NES and Nintendo 64 (Metroid Prime, the Zelda bonus discs, Animal Crossing), so about all they need to do is get a good SNES emulator working to cover all the TV consoles. They also have the Game Boy aspect covered with the old SNES adaptor, and also the Game Cube adaptor for the GBA games. So for the most part, not much work needs to go into the emulation software for the Revolution.

As far as what console will be a good media hub, it's hard to say out of the box. The XBox already has the Media Center expander stuff, and so the 360 will as well. The Playstation 3 I bet will have several features in line with the PSP, but expect typical Sony crippling here. What the mod community does is a whole different issue, but I am guessing most of the modders will target the new XBox again if it ends up the only console with a hard drive by default.