I love Nintendo and SEGA equally, and find it impossible to say which is 'better'.
Looking at it objectively, Nintendo's very best games were probably better than SEGA's, but SEGA made many, many more games in a much wider variation of genres.
How can I possibly say whether I had more fun playing Mario, Zelda and F-Zero, or Sonic, Virtua Fighter and Panzer Dragoon Saga.
Sadly, I've gone from being a Nintendo fanboy towards the end of the 16-bit era and through the N64 days, to being someone who couldn't really care less whether or not Nintendo releases another console. For me, the Gamecube software library has been a bit of a joke on Nintendo's part... Mario Sunshine wasn't as good as Mario 64, F-Zero wasn't as good as F-Zero X or F-Zero SNES, Mario Kart: Double Dash!!! wasn't as good as Super Mario Kart, Wave Race: Blue Storm wasn't as good as Wave Race 64, 1080 Avalanche wasn't as good as 1080 Snowboarding...
The Gamecube is a really great machine - the hardware itself is gorgeous, the visuals are solid and vibrant, loading times are fast. In fact it's probably the overall best designed piece of kit out there right now. And all those titles I've listed are good games, but where's all the innovation that Nintendo used to have? I truly hope that Revolution is, just as it's name suggests (especially for all those Famitsu readers), a revolution in gaming, and that it gives Nintendo to opportunity to bring back some original gameplay ideas. Unfortunately, I'm worried that the company might be going down a niche route if the rumours about Revolution's design are to be believed. I'm fairly certain that, unless Nintendo can market it just right, the mass market could see the machine as being gimmicky. Still, it's not really for me to comment on until the final design and specs have been unveiled.
And as for SEGA these days... well, since Panzer Dragoon Orta and to a lesser extent, Out Run 2, the company might as well have closed down. But the brief videos of Sonic, Virtua Fighter and House Of The Dead that were shown at E3 looked promising, so we'll just have to wait and see.