You guys should play Eternal Darkness or any of the Resident Evil games on Gamecube and you'd lose the kiddy image of it immediately. After beating Eternal Darkness, I looked at the GC as a reminder of a game that scared me shitless.
PS2 and XBox has as many kiddy games as Gamecube has...they simply don't have as many old-school mascots that appeal to younger people. I personally have no qualms with kiddy-games as long as they kick ass. With Shigeru Miyamoto heading up most of the "kiddy" games, they turn out to be masterpieces despite their marketed audience.
-Lasereth