MEGAT0N!!
But seriously, Nintendo covets Super Mario Bros 3 in a way that I have rarely seen from them. Probably because not only is it the top-selling non-bundled game of all time, but you could say that, from a technical perspective, it's the most flawless game ever made.
Even when Nintendo was going crazy with their Mario rehashes/re-releases/remakes, SMB3 was protected like a sacred cow. On the GBA, for the Classic NES Series, nearly every major Nintendo NES game was ported, the original SMB, SMB2, Zelda I and II, Metroid, etc. Yet Super Mario Bros 3 was never released for the series - it was too precious to Nintendo.
Then, for the Mario Advance games, first they remade SMB2. Then SMW. Then Yoshi's Island. But SMB3 was saved for a year more until it was remade as Super Mario Advance 4 in October 2003.
And finally, the Virtual Console. By now, nearly every top Nintendo game has been released, except Super Mario 3. Nintendo was either saving it for the worst drought the Wii will ever face, to use it as a crutch, or for the release of Galaxy. That's how highly they regard it.
Anyway, I'm glad it's coming.