If you're talking about games that anyone - not just gamers - can recg... recz... ah, screw it - identify, then Sony's household names would be Singstar, Buzz and GTA, with LittleBigPlanet being a potential candidate if it manages to even somewhat meet its hype. Other IP's don't have a chance of achieving this.
If you're meaning "gamer only" brands, Sony has quite a few of them. The problem is that:
1) Sony (or a valid 3rd party company) is pretty much already investing in every somewhat valuable brand it has. Unless you're doing something like Smash Bros. it's pretty much a waste of time, money and effort to raise stuff like Wipeout from the grave.
2) Most of Sony's new brands either don't exist yet, or are in their first or second iteration. Building a brand takes a while, and also requires consistency, both in the number of released titles and quality.
3) Every new, somewhat important, PS release is being hyped to the moon. This creates unrealistic expectations for every new IP, and if (when?) they fail to meet those expectations, it hurts both the IP and the PS3, sometimes irrevocably. I know you're supposed to promote your game and bribe the reviewers to make them sell more, but goddamn, enough is enough.
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