Yeah the N64 was great, but in total worldwide console sales totals, PS2 = 155 million, N64 = 33 million, Dreamcast = 9 million. Partly the enormous total was because the PS2 stuck around for so long (and, cyclically, kept getting games for ages because of the installed base) but my point is, for most gamers, it's more like they didn't have a Dreamcast because they had a PS2.
That console generation had a clear winner, despite Nintendo doing its own wonderful thing as usual. Sega were out of the running, due to bad previous consoles, price, Sony's frankly dishonest publicity about what the PS2 would be able to do, some great hits coming to PS2 first, the DVD drive, and just the general network effect that means the winner of a format war sells many more units.