We all like to say that Nintendo's 3rd party support was at an all time low during the N64, but looking at the titles we got, it wasn't really that bad. I also really don't understand how this machine had acquired the stigmata 'kiddie machine' by the end of its life cycle.
The N64 had decent 3rd party ports, like THPS2, we had sports games from NHL to Fifa, awesome ports like Rayman... but this thing was a monster shooter machine! It basically cultivated the Xbox demographic before it came to be.
It had an exclusive Doom, Quake 1, Quake 2, Hexen, and the exclusive Duke Nukem: Zero Hour, Turok 1-3 and Rage Wars, Daikatana, Duke Nukem 3D...
Besides that it had Shadow Man, Armorines, Body Harvest and the Mission Impossible games, it had for some weird reason Command & Conquer and Starcraft, it had the exclusive LucasArts games...
And this is all just western stuff, Bomberman was basically a Nintendo Icon during this time with 3 exclusive titles and Konami also had the 3D Castelvania titles going..
You get where I'm going. The titles weren't that well paced during it's life span, some titles where of questionable quality and hindsight is 20, but there are many titles I look back on fondly besides the obvious Nintendo titles.
I'd say that the shutdown of their American 3rd Party team, when Nintendo Japan/Iwata took the helm during the GCN era was one of the biggest mistakes Nintendo made during their last few generations.
I don't know if their relationships to the western dev teams were better than they are now, but they delivered results considering the Playstations 3rd Party policies were much better, the cartridge situation and that they were late to the generation.