Nintendo tried this as recently as the early 1990's (yeah, been awhile).

The problem has always been that Nintendo licensed out their characters to other companies rather than handling the programming and such themselves. Sure, the first method is easier on Nintendo but it also leaves a bad taste in their mouths for such efforts as not all companies have the resources to "do it right".

Anyone play the Super Mario Bros on PC-88?

Not a stunning effort by Hudson Soft. The ones by Phillips for the CD-i are not much better (and they got Zelda too).