Nintndo gives proof of third party Wii sales.

[LordTheNightKnight]

Here's That Wii Third Party Sales Proof You Requested

This is the first 19 months for each system, but even when the system launched, Wii third party games were still selling between 360 and PS3 third party games. After Guitar Hero III, Wii third party games took off (although that helped the PS3 third party games as well).

Of course since this is on Kotaku, the fanboys changed the line from just straight "Third party games don't sell on the Wii," to "What is the attach ratio?" (which is stupid, since the PS2 and GC had nearly the same attach ratio, and we know which came out on top), or "Show us the Metacritic scores! This will prove it's all shovelware!" (also stupid, since not only are the overall Wii reviews only slightly lower than the other systems, the term shovelware means slapping software onto a disc, not whether a game is made for less than severl million and made for casual adiences).

What this chart does prove is that games do sell on the Wii, even by third parties, so claims you can't succeed on the system are really shaky (especially if Ubisoft is still spending lots of their casual game money to fund Red Steel 2).

This also proves that with so many games sold on the 360, and this only covers the first 19 months, it's more likely just raw sales potential was the factor in FF XIII going multiplatform.