I'd like to see J.O. back/compat just for you guys!
It's a great game but looks and plays fine on my old xbox and my pc version. I'm never in a hurry to see a title go back/compat unless it can do widescreen. Otherwise, they almost look better in 4:3 on the old machine anyway.
As far as Oucast -vs- Academy goes, here's my take...
For the xbox, Outcast is a GREAT single player campaign. Academy on the other hand, is less like a sequel and more like the online multiplayer component or extension of Outcast.
Though they are apples and oranges, you can't fully enjoy one without the other.
My advice... if you've never played either, start with Outcast. Once you beat the campaign, hop online with Academy. They're both great in separate ways.