In terms of sales, it was the generation that was a complete rout. The PlayStation 2 was just a ridiculous, runaway success. Nothing could compete. But the race for second? That was far more competitive. Which console did you prefer? The GameCube or the original Xbox?
I could legitimately make a case for either.
The GameCube had arguably the best line-up of exclusives of any console ever made. Metroid Prime, Wind Waker, Pikmin, Mario Sunshine, Resident Evil 4 (for a while). The Xbox had the Halo series, Fable, Ninja Gaiden, Splinter Cell.
The Xbox was a powerful machine that ran multiplatform games beautifully and the GameCube had some seriously innovative technology glued to its innards.
As much as I loved the Halo series, my call would have to be the GameCube. The exclusive line-up was too powerfully awesome. There's the ones I mentioned above, then there were the outliers: Mario Kart: Double Dash, Super Smash Bros. Melee, F-Zero GX. Yep, the GameCube had some serious exclusives.