[quote name='Limpbizkit182521']Actually the PS2 version sold pretty good compared to the PS3 version. According to VGchartz.com:
PS2 version sold 400,000 copies
PS3 version sold 630,000 copies
360 version sold 1,560,000 copies[/QUOTE]
Or to put it another way, the PS2 version has sold the worst.

230,000 less than the PS3 and 1,160,000 less than the Xbox 360. What really matters, though, is inventory. Presumably they overestimated the sales of the PS2 bundle, and did better with their estimate of the sales of the PS3 and 360 bundles. Hopefully 400,000 is enough to justify producing more (or any) add-on discs for the PS2 (the first one could yet be canceled, but I hope not.)
What will be really interesting to see is how well the Wii version sells. In terms of consoles out there in use, the Wii should then see good sales, but on the other hand it's neutered just like the PS2 version and yet doesn't have the advantage of the instruments being compatible with some other platform too, that the PS2 version does. Actually I only say that in theory. I wouldn't be shocked if the instruments are really all compatible with each other. They all plug in via USB, so they could be compatible (will the Wii version plug in via USB? I guess they might not) and it would be easier and cheaper to make them all compatible (why have different code on different platforms when it isn't necessary?) I think the only difference may be how they've labeled/colored the buttons. Somebody needs to test it out and see.