I know people that doesn't give a damn about mainstream console games (hello Xbox), that are waiting for The Last Guardian to release since Team Ico games were the only reasons for them to buy the PS2. So even a niche title can push hardware / make an impact.
Think about it this way: Sony is competing with MS in the "HD Wars" and Sony's content tactic is diversity and niche against MS's mainstream. That's why Sony supports interesting exclusive titles be it 1st or 3rd party (Demon's Souls, Heavy Rain, TLG to name a few). Now these games may not sell gangbusters, but they have an audience which won't buy the Xbox, because it's titles aren't interesting to them. As Jack Tretton said during last year's E3: "Our customers aren't one trick pony".
And as you can see, it works. People generaly prefer something new (atleast relatively), to milked franchises over and over.
MY HYPE LIST: 1) Gran Turismo 5; 2) Civilization V; 3) Starcraft II; 4) The Last Guardian; 5) Metal Gear Solid: Rising
