PSX was better at the time, but the N64 multiplayer games have aged really well. When I list stuff on PSX that I still play with any regularity, it's a handful of RPGs. When I do the same for the N64, it's a few single player games like OoT and OB64, and a bunch of multiplayer games. Really the only comparable thing the PSX had was Crash Team Racing. And while that game is really good, it's also only one game.
All very true. There's also the fact that the PSOne library is designed around two controller ports as opposed to four, which really limits multiplayer potential.
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The Many Forms of Kobe:
http://i39.tinypic.com/oqx98z.jpg -- credit to KIRBEH