That really is the difference between the Wii and the PS3 to be honest:
Wii needs to get as much 3rd party support now as possible due to the fact that it will need to vastly expand its game library. History tells us that the console with the most 3rd party support invariably comes out the winner (NES,SNES,PS,PS2) so if they want to win, they need to reach out to others which thankfully they are doing.
The PS3 on the other hand needs to keep as many 3rd party companies on its side now because the true power of the PS3 (games wise and sales wise) is in the future. The sales will increase and it will generate more 3rd party support which will be the catalyst for improved sales.
Games i'm currently playing:









