The simple answer to your question Joelcool7 is that when Nintendo launches a new system they need Mario or they need a killer app like Wii Sports.
Zelda did not sell the Wii, flat out, no.
Wii had instead a killer app in Wii Sports. Without that killer app, and because of no Mario, Wii would have had a much different launch.
It's would be a risky thing for Nintendo to launch without Mario because then they'd have to rely on that killer app which _is not guaranteed_ to work. Early adopters, AKA people who like Nintendo already, are the core, and expect certain things from their purchase will think twice about buying at launch or in the early months unless there is something compelling.
Very little other than Mario and to a much lesser extent Zelda appeals to this core in any great number.