I guess the real question is how you define victory. I know Nintendo got me to open my wallet much more often than SONY or Microsoft. My personal preference for the three consoles is GameCube, Xbox, and a distant third the PS2.
PS2 obviously dominates in regard to third party support and the volume sold, Xbox is the most powerful console, and while I know my opinion is in the minority, Nintendo continues to offer the most polished and most captivating software for my gaming interests.
So while the general public has thrown their support behind the PS2, the GameCube remains my platform of choice for this generation.
Looking to the future I believe Microsoft will be the overall victor in the next generation. Despite this belief there will be a spot reserved on the top shelf of my entertainment center for Nintendo's next console. As dpatel said above, depending upon how "revolutionary" Nintendo's next console is, it could be hit or miss. Either way, since it will be the only place to play the next Mario, Zelda, Metroid, etc., I will own it. The real battle for my gaming dollar will be between Microsoft and SONY for the right to sit on the shelf below Nintendo's next console.
With all that said, by most measurements, the PS2 easily won this battle. Even with multiple PS2s sold due to defects, you only need to look to software sales to know SONY has far more consoles in use than either Microsoft or Nintendo.