Yeah, although I didn't like it, Nintendo's decision to cut second parties loose seems to have worked out very well. My thoughts at the time were that Nintendo was giving up a lot of exclusive properties - Killer Instinct, Banjo Kazooie, Perfect Dark, etc. However, as Sony vs. Nintendo has shown, a large stable of long-time exclusives isn't everything. Take Crash Bandicoot and Resident Evil from Sony, and five new games take their place (such as Jak, Ratchet and Clank, Fatal Frame, Devil May Cry and Ico).
Nintendo has enough long-time properties in it's collection without buying more from second parties. The only way to hurt Sony is to turn things upside down so the massive third party support moves in your favour. So far I think Wii is doing a hell of a job on that.