A bit of an old article, but a very good read-
http://www.gamesradar.com/xbox360/f/why-xbox-live-isnt-free/a-20080617101147502012/p-3
Essentially what Xbox live offers, PC/PSN/Nintendo offers for free. The only thing you could say that XBL has is a solid interface which the competitors don't have, but then again, I don't think MS needs $50 per year to create a decent interface for its users to use.
But really what live is doing is benifiting the individual game developers rather than the actual consumers. This is because when we pay for live, a substantial amount of the money is used by MS to host servers and take care of the online infrastructure of games. The same can not be said for PSN where the developers/publishers have to pay money from their own pockets to keep the online going for games. So in essence what this does is allow for smaller developers of XBLA+Indie titles to create solid online experiences. Also bigger publishers prefer the Live infrastructure more and problems are fixed much quicker on XBL regarding online games, as they have more incentive to do so.
So overall, live does encourage more developers to create unique titles and the question is whether or not it would have been possible without MS charging money for online play.
