The N64 was the first nintendo platform to support a C compiler out of the box.
I suppose it's possible that some crazy developer wrote their own C compiler back in the day, but if that ever happened I didn't hear about it. And I was trained by people who worked for Nintendo.
The PS1 was released before the N64 and supported C compilation. In fact, in the early days Sony didn't want people to use much ASM because they were worried about backwards compatibility on future systems. The PS1 port of Doom suffered from a lack of assembly optimization.
Gran Turismo and Metal Gear Solid were written in C. Ken Kutaragi used them as examples of what could be done with efficient programming techniques and good use of Sony's performance profiling tools. (citation needed: one of my old gaming mags that's probably been recycled three times over by now)
It's rather interesting how Sony went from starting with a system that was considered easy to develop for, to having the most complex product on the market--twice in a row!
Not that that wouldn't make this presentation here an impressive feat.
[0] http://www.metroid-database.com/m1/sourcecode.php