I agree that weak marketing has affected them to some degree. They have high profile titles releasing every few months, sometimes more often that that (like last holiday season). They should be capitalizing on this more.
Great marketing per title helps them in two ways:
1. It improves the sales (or sales potential) of the marketed game.
2. Given how often they have exclusives coming out, it gives people the impression that the ps3 is where the big exclusives are. If every couple of months you see TV ads for yet another big ps3 exclusive all over the place, it gives you the impression that the ps3 is where the games are, even if none of the games shown in particular are your cup of tea. People'd be saying "Damn, another game only on ps3?"







