gamecube all the way.
ps2 is a joke. dreamcast was (sadly) a failure. xbox is microsoft... who knows EVERYthing about marketing and advertising... but NOTHING about games.
nintendo is really the only product that will truly kick ass. they've always had the games and designers to make theirs the best, now they have a superior console, as well. hands down, ngc wins.
gba is a seperate deal, and, im torn on whether or not ill get it. i want it, but... dunno if ill get as much use out of it as id like. and, with my soon-to-be slim budget... well... we'll just have to wait n'see.
as far as sega partnering with others... truth is, they'll partner with no one. they'll produce games that will be picked up on all systems. as of now, they're supposedly linked with xbox, but only because xbox is releasing all their info, hoping to "hype" sales, like sony did/does. believe you me, they're also designing for nintendo. whether or not those games will be made final, i have no idea. but, as it stands now, they have as many plans for gc as they do for other systems (computer dork cuzin thatchya met just found out).