@ Avinash_Tyagi
Nintendo and Sega were the market leaders when the Playstation launched.
Nintendo platforms traditionally show relatively high early adoption ratios (they discontinue their consoles while introducing a new platform at mass market entry pricing and release content appealing to the former userbase fairly quickly like Mario and Zelda games), be sure that many GameCube users bought a Wii to play the latest Mario, Zelda and Metroid games. The Wii is doing great, especially by expanding their market next to making Nintendo fans upgrade towards the Wii.
I think things will get more difficult later on as more people are becoming more interested in high definition content and technologically more advanced games and by the end of this year the bulk of Nintendo fans will own a Wii already. The Wii is a platform which has almost no overlap with the PS3, if you look at the top 20 best selling PS3 and Wii games there's no overlap there apart from Guitar Hero 3! Thus it's not weird to imagine many Wii users will also own higher specced platforms eventually.
