Well, Sony and Nintendo both boosted the series at one time or another - Square's NES games never even would have appeared in North America if it weren't for Nintendo - but KDR is basically right, Square deserves 95% of the credit.
Determining which half of the series is more important is also hard. Most people here will pick the first half, being Nintendo fans and prefering gameplay over movies. I think the sales numbers support the second half, though, especially Final Fantasy VII.
I'd kind of like to see a Super Mario RPG 2 as well. I used to shoot that request down because I'm perfectly happy with Nintendo's Mario RPGs, but with Paper Mario and Mario and Luigi reaching five games in total, it could be an interesting change of pace.