If a Wii game sells about 300k worldwide then it can be called a success. 500k I guess for a huge production value game and 100k for one that's well shovelware. Sometimes even less. But most are looking for 300k.
Such as Rayman: Raving Rabbids has sold 1.16 million on Wii. The profits Ubisoft has made off this game must be really really high cause development cost for this game couldn't have been much.
RE4: Wii Edition has sold 1.03 million units. I bet it only needed like 150k to break even. Capcom has made a killing off this. Red Steel probably needed 500-600k. So Ubisoft still made profits.
But right now easily the 3rd party game that is probably making the most money is Mario and Sonic at the Olympics. Although the game is part Nintendo, it is published by Sega. This game was probably a 300k profit game, and man its skying past that. Going to see some Sonic and Sega love for Wii.
I could name a lot of games on Wii that have done well for 3rd parties. In essence compared to when games make a profit, devs are doing quite well on Wii. The only game I can think of that caused probably a loss is Manhunt 2. And that's for obvious reasons of it not being a very good game but had high production value, and all that other crap around it costing more money.
