IT's not that the developers don't want, it's that the publishers darn't risk money on a new IP or idea. At the end of the idea it's much safer going for a market that already exsists and putting one unique 'spin' on the basic concept for uniqueness - and the formula seems to be working. With so much money involved I don't think anyone out there seems to dare risk it on something unproven, outside of Heavy Rain and The Last Guardian, and a few others.
The Downloadable platforms do remedy this a bit with some brilliant content, but when it's at such a small scale it's hard for it to really embed itself in your memory as the greatest games of the year, even if it's really really fun.
Unfortunately Sales trends are going towards an industry which is going more iterative by the year - the big hits were all sequels (many yearly releases) like COD, Halo, AC, FIFA, Fallout etc whereas anything with a hint of originality or at least trying to do something slightly difference bombed - Vanquish, Blurr, Enslaved. Hell those games didn't even stray very far from the tried and tested big-hit seller formula, so it just shows how much risk there is.
To try end on a positive note, I think we are seeing occations where by making a game 'different and interesting' it can spark the imagination of the gaming audience and lead to an unlikely hit. I'm sure every publisher suit-guy who makes the decisions on this sort of stuff would have scuffed at the idea of Heavy Rain ever having a hope in hell of being a hit, but alot of people bought it - COD / AC type yearly buyer people - simply because it was something different, and the marketing did a good job at getting that across. So there is hope.
