I think the Gamecube strategy is something Nintendo should look at in the next few year, at least when it comes to specs. Maybe a less goofy design (though goofy as it is I love that little purple box) and obviously don't cheap out like the mini-DVD, just give us a Blu-Ray disc playing Nintendo system.
The Gamecube's third party support wasn't the best, but it was a solid step in the right direction. I will point out that it's a bit unfair to talk sales in relation to that generation because it was pretty much "meh" for anything not named the "PS2". The Dreamcast crashed. The Gamecube declined, and even the original Xbox didn't sell all that greatly (not to mention it was much more expensive for Microsoft). Sony just had a huge grip of the industry that generation.