these download games are normally classics,updated a fair bit,but the basis remains the same. the asteroids is to die for.full colour,better graphics but the same basic system.
it seems to be an angle to compete with the could be killer apt of the nintendos ability to download every game they ever made online.(WOW)
as for rebellion,they may not have a big enough back catalogue to covert,and to create platform versions of the others games could well delete royalites for them,there are JD gameboy games and PS1 games about which can be found on the net already to play on the pc.
rebellion whilst a decent company may not have the resources of say EA to do such a thing.given its potentailly low selling market. the world played asteroids,space invaders,pinball but only a handful of us even know who Slaine is.
we shall see,but they dont have a great track record on the LIVE games yet.even sniper elite(very recent realease and pretty good,) is not a huge hit on live.