|Pyro as Bill said:
Yeah because the multiplayer in Wii Sports really hurt Mario Kart Wii which in turn damaged Wii Sports Resort sales, right?
Poor NSMB Wii had to compete with all the above which is why it hasn't beat MW2 combined yet.
Nintendo are so stupid for releasing multiplayer games. Hopefully they realise their mistakes soon so that they can sell more software. They also need to start charging for online otherwise the decline in gaming will only get worse. Oh and used games, let's not forget used games. Nintendo should start fining people who buy used.
Gotta save the undiztry.
Judging from the decline in Wii software we're seeing on a monthly basis I'd say your thesis is spot on.