i have been wondering this as well for some time now. both MS and sony have to sell more to make up for the higher hardware cost. i also wonder if sony needed to raise the royalty rate for third party publisher because of using blue-ray, i believe the rate in the last generation was around $7.00 and by using the same media format i believe that MS could use the same rate.
i do believe there are a few games at the ps3 launch which will get good sales/attach rates. CoD3 looks to make an even bigger impact in the next gen scene then CoD2 did and that sold great, resistence is another game that looks like it will gather a good amount of attention. however with the huge gap in the install base, im sure more publishers are relying more on the 360 version of multiplatform titles for the sales.
another thing i wonder is how soon/long until we see the ps3 crack the 10 game sales list. the 360 did far better and faster then even i suspected. activision, ubisoft, and 2k all credited the 360 for great quarterly results because of the respected launched games (CoD2, GRAW, and oblivion). i also wouldnt be surprised if sony came under more scrutiny (spelling) or critisizm (again spelling?) because of the additional cost to develop a game on the ps3 which would raise expectations (or numbers at least) for publisher to sell to break even and make profit.