The problem is, that exclusives do define the console. For instance, take Xbox and Halo. The Xbox was doing decently and once Halo hit, Xbox skyrocketed. Granted it never beat the PS2, but 1 game drove its sales up by a long shot. Halo 2 had the same effect and I guarantee that Halo 3 will have a similar effect on the Xbox360.
And to clarify why the PS3 is losing exclusives really has nothing to do with the Cell processor being more difficult, as IBM has released learning materials for free and has conducted many classes on teaching Cell programming to developers.
Instead it is the USER BASE. Out of the three consoles Sony has the smallest user base. Game companies want to earn money on their products, so rather than make a game that only 3 million will play on the PS3, they'll make it for the PS3 and Xbox360, thus having a maximum of 13 million players.
I know money is the reason why they do that, but the logic behind it escapes me, since games rarely sell a million copies within the first 6 months to a year. Chances are most good games only ever sell 2 million units...