Sega arguably failed because they kept releasing stuff (MegaCD, 32X, Saturn) and dumping it early, thereby losing consumer confidence. That and all their Commodore-esque internal issues. Their hardware wasn't necessarily underpowered - the Dreamcast was pretty good actually.
Nintendo seem to have done OK with their last few console releases selling 20-40 million, which almost puts them in niche status anyway. I'm sure the Wii will sell just as many if not more, and Nintendo are going to support it properly, unlike Sega.
Nintendo seem to have done OK with their last few console releases selling 20-40 million, which almost puts them in niche status anyway. I'm sure the Wii will sell just as many if not more, and Nintendo are going to support it properly, unlike Sega.