I think we can safely say in this console generation that games do not drive console sales enough to make a difference. If this was the case the PS3 would be gaining steam as the quality of releases for this year and last was matched by no other console on the market. For 2009 and 2010 it's looking like an even larger gap between the ps3's quality games and the competitors, at least considering announced titles as of right now.
This console generation is interesting, since gaming is now the popular thing to do in life, and no longer a nerds hobby, sales are vastly driven by what the cool kids at school have. I would assume most of XB360 sales come from people who only care about having the same console everyone else at school does.
But what do I know, I've been out of high school for longer than I'd like to think. Still, that definitely has a large push, it's the only reason the xb had any sales at all.
Not to say the 360 doesn't have games for everyone, because it does, and great ones too, but you know very well that out of the 10million halo fans, about 1million of them are real gamers. I honestly think people underestimate the influence of halo, it brought gaming to the casuals of the world, and made them think that they were real gamers. It created a generation of people who play nothing but halo and gears. Actually, the sales and success of the XB360, and the sales and success of the gears of war franchise are almost completely because of Halo. I Would even go as far to say that call of duty owes a lot of its success to halo as well. It's really interesting how much influence a casual shooter can have on the gaming industry, and I hope to see other companies design games similarly. (ie; masking a hardcore genre with a casual game) Would surely open up more doors for other genres to gain an audience.
I think while sony will keep pumping out incredibly high quality games year over year, and will remain THE console to own for the best games as it is now, it will never catch up in share because without a game that draws the casuals to its platform like halo, sony will never be able to gain the interest of millions of children like the xbox360 has. Why would they want a PS3? No ones going to brag about getting kills in resistance in a school locker room, even though it is an infinitely better game than Halo.