The reason it takes Nintendo longer to develop games is because of their policy to not release games unless their perfect.
I read a rumor that Pilotwings Wii by Factor 5 was finished but Ninty refused to release it since it was bad.
I think Ninty should build development teams from the ground up and expand their existing teams with more talent. I also hope Nintendo doesnt try to emulate western developers with their male power I'm-a-bad-ass type games. Ninty should stick to their innovated, light hearted games. That is why I think Ninty is so successful because everyone else are making those games which whereas Ninty has less competition with their type of games.