I really don't think you can blame poor third party sales on Nintendo consoles on Fanboys so much as 3rd parties and nintendo itself.
Fact 1: Nintendo got very cocky and alienated many 3rd parties Square etc.
Fact 2: When Nintendo get's a 3rd party game it's often a port of a game already existing on another console or a game that's going to come out on another console in the future usually with a simmilar or larger user base so naturally sales would be better ( Resident Evil 4, Manhunt 2, Marvel Ultimate Alliance, are good examples)
Fact 3: Normally 3rd parties don't seem to use the extras available on the nintendo games to their fullest, compare DS/Wii games from 1st party to 3rd party there is a difference of use in most cases the 1st party use them better.(not ALWAYS)
Fact 4: 3rd parties sometime put spin offs of their popular games onto Nintendo consoles (The only good example I can think of is Final Fantasy Crystal Chronicals.) more often then not these games just pale to their original series.
Fact 5: A lot of times 3rd parties but their 2nd 3rd and even 4th tier developers onto projects for nintendo consoles(This is only showing up recently on GCN N64 and kinda unsure about wii I haven't really looked.) The point is putting a B or C team on a game expected to compete with a popular software makers A team is simply retarded.
I think the 3rd party sales are a fault of Rabid fans, good titles vs poor titles(Nintendo normally makes some damn good games but wtf is with mario playing sports?!) and probably a lot of other stuff we can't see without being in the buisness. Just a thought though...