You have to think about a lot of things in this question...
If Nintendo was new, and did the exact same thing (advertizing etc) Gamecube would have been dead already... why?
1) Nintendo didn't pay for third party support like Microsoft, and Gamecube wouldn't have gotten half of the support it has now.
2) People would judge Nintendo by there first party games... Luigi's Mansion would not be the record holder for most launch sales...
3) Nintendo's main games are sequals... Smash Bros, Rouge Leader, Waverace, NBA Courtside, Etc... If Nintendo was the new guy making these games, these game would be considerd a Joke, like Ampped, NFL Fever, and NBA Inside Drive for Xbox.
4) Nintendo's advertizing campaing was weak... if you lived in a city with a Cube club, more power to ya, but 95% of the country doesn't even know what the cube clus are, and they will probably will never know... They needed a better place for Hype (Taco Bell maybe?
)
But I dunno, if Nintendo was the new guy, there advertizements and games would have been a lot different... it would have been a lot more like Xbox... and Nintendo would have spent more money...