I don't think there is a need for a "must own" PS3 title . When you think of XBOX 360 most people are thinking Gears 2 or Halo 3 in terms of "must owns" as soon as you eliminate one of these guys you loose a big incentive to buy the XBOX 360 , the brand has effectivley placed all it's eggs in one very big basket.
The playstation brand is defined by various titles Resistance 2 , Little Big Plannet , Killzone 2 , Gran Turismo 5 , God Of War 3 and the list literaly goes on . Some are must haves wheras others are decent games at least , the important thing is that Sony's hasn't placed all their eggs in one basket they've gone for diversity and consistent quality , an approach that imo is better for apeal on a mass market level ; the console offers huge incentive across a range of titles.
What I think the PS3 continues to lack is an affordable price point , arguable the biggest problem and the biggest solution.







