If you compare the tie ratio instead of absolute sales, you'll see that many multiplatform games sell better on PS3 than on 360 (even GTAIV, for example).
Plus, it actually makes sense distinguishing the regional submarkets. Japanese gamers are not going to buy CoD games and europeans won't go mad over a Madden american football title.
The X360 being NA-focused makes a big difference on these titles.
The Wii is a different beast, again because of sub-markets. Some multiplatforms sold less on the Wii because they were either catering to a small subset of the huge install base or a gimped version of the one available for other consoles. Combine those two in the fact than many Wii "core gamers" also have one or both HD consoles, and you'll see that even they might prefer a different version.







