NSMBU did have graphical improvements, though... as well as some new gameplay aspects. Saying that, N64 probably wasn't the best console to bring up, considering there was no 2D Mario on it.
Also, why didn't you just buy another Wii? It would've been cheaper and you could've just played the games you originally had. You wouldn't have to bother with updates or any of the new and "improved" HD shovelware. (Which plagues every console, by the way.)







