Can't Capcom make a contract with Sega were they release their Saturn library onto Xbox Live?
I have to say that the benefit of PSN is the immense library of titles from the PS1 at Sony's disposal.
Wii has the Virtual Console which, of course, means Nintendo can release games from the libraries of previous generation consoles (including Non-Nintendo consoles).
This is were Xbox Live fails in comparison. If only they would offer similar products. Although when it comes to social networks, Xbox live is evolving (specially with the coming of Facebook and Twitter).