No, they do not.
Again, have you seen these awesome discount games crack the NPD Top 10? No, you have not. I think the only successful third-party title in recent memory, outside of Guitar Hero, was Carnival Games.
It's as Third said, you have a lot of third-party shovelware selling for $19.99 that move 20,000 units a pop, but nothing that generates a great deal of revenue or sells in the millions. Third parties recognize their hardcore constituency is on Microsoft and Sony's platforms, which is where they will push a 1 million+ units, but the Wii user base is too large to ignore. You'll continue to see stuff like Dead Space: Extraction, Wii-ized spin offs of popular properties because direct ports, like Dead Rising, will tank.