Wii sells more games per user then the PS3 in Japan. The real for the third parties is that the Wii audience is more divided due to new expierences.
Things like Wii Sports Resort, Wii Fit and Super Mario Brothers Wii and such are going to take away from your midline franchises. Not Final Fantasy.
This same statement could've been made in reference to the ps2, yet all these franchises sold far better there than they do on the Wii. On the ps2 there was a endless avalanche of new games to play in Japan, yet these franchises still managed to make names for themselves. There's more to this than there simply being more games to choose from on Wii.
Also, your Outbreak comparison is confusing. The games are fundamentally different (and Outbreak is far, far closer to the "mainline" formula in terms of mechanics and presentation), what you should be comparing are the lightgunners... Famitsu data again..
We don't seem to have any data for the lightgun series in our database, which is why I went for the only other Resident Evil spin-off I could think of. It was a rather ill chosen comparison, I agree.
Keep in mind that with older lightgun games you actually had to buy the lightgun in addition to the game. With the Wii, you simply use the standard controller, which is why lightgun games have shown far greater success on the Wii than ever before. The Time Crisis series did pretty well on the ps1 and ps2, but that was the only big thing since Duck Hunt. The Wii's success in this regard has little bearing on where the Resident Evil fanbase now lies.
The PS2 port of RE4 was announced before the GC version released even, it totally killed it's sales potential since pretty much everyone already had a PS2. Had the port not been announced, I think you'd have seen a ratio split more in line with what we saw for Tales of Symphonia (did 323k GC, 394k PS2).
This is an excellent point, and one that I had completely forgotten about. It basically invalidates the example I used.