Its funny that you say "Wii doesn't need third party support to succeed," but if you added it, it would have by far the biggest amount of third party exclusives.
I don't care if you just want to look at 360 and PS3, but you can't really say third party exclusives aren't needed by Wii until you examine the facts.
I'll just look at one month: your first month being examined of October 2008... In that month, in America, Wii had the following third party exclusives... I don't believe I've listed all of them, but just ones that stood out as being fairly major from Wikipedia's list:
Game Party 2 (the original sold 1.49m)
Boogie Superstar (the original sold 430K in the Americas)
Carnival Games: Mini-Golf (the original sold 2.43m)
Jillian Michael's Fitness Ultimatum
Naruto: Clash of Ninja Revolution 2 (the original sold 880K)
All-Star Cheer Squad
Ben 10: Alien Force (the last Ben 10 game for Wii sold 810K)
MySims Kingdom (the original sold 1.27m)
So that's 6 exclusive sequels to exclusives which sold at least 800K copies on Wii, 4 of them million-sellers, and 8 total games which should be watched to sell 1m copies worldwide, just from October.
Granted, October is the biggest release month of the year, but nonetheless, that's a good haul. The big difference is that none of these will launch to millions of units like some big 360/PS3 multi-plats do, but take months and months to approach 7-digit totals. But nonetheless, it seems to me that third party exclusives are pretty important to Wii.
"[Our former customers] are unable to find software which they WANT to play."
"The way to solve this problem lies in how to communicate what kind of games [they CAN play]."
Satoru Iwata, Nintendo President. Only slightly paraphrased.
