I guess it shouldn't surprise me that the Duo pack-ins are annihilating all the other choices. It is, after all, a TurboGrafx forum.
But I doubt that'd be the case on any other video game forum. As much as I love the Turbo, objectively speaking I think Mario 4/SMW is by far the best pack-in ever. I mean, that game was f*cking phenomenal. The amount of work that must have gone into that game... only to have it end up as a pack-in. They could've sold the SNES without a pack-in and made people cough up $60 for Mario and made a killing.
I guess it depends how you look at it. Quantity-wise, sure, the Duo pack-ins would slaughter any competition. But on quality alone Mario just kills. It's probably as close as you can come to having a "perfect" platformer. And they just gave it away for free.