Do you mean best console out right now? Probably the Dreamcast. It has the best price and is the best deal you will ever find for good videogames. Or do you mean the one with the most future potential? Probably the Xbox. Or do you mean the console that's the most popular? The probably the PS2. Or do you mean the console that has the best first party developers and support? Then probably the Game Cube shortly followed by the Xbox (since Sega only really supports the Dreamcast in Japan, I'm not going to count it as first party supported).
Which would I rather play? Depends on the game. Final Fantasy? Well I have only one choice don't I? Halo? Well I have only one choice don't I? Smash Brothers? Not much choice there either? Sakura Taisen 4? You guess it. One choice.
As for the GBA, the GP32 is a better machine, but the GBA has more games and support.
