A modern 3D Mario with the same semi-open-world structure of Mario 64 as opposed to the more linear levels of the Galaxy games.

I don't think it would've mattered much either way to be honest. And 3D World was an excellent game not sure why some Mario fans don't like it.

I agree it was an excellent game, but I don't think it's so much Mario fans that don't like it, it's more mainstream gamers that found it's modest, conservative presentation and scope to be underwhelming compared to the Galaxy games or 64. 

I don't think there are enough people who care about that difference to make any real difference in sales.

Though, for my money, the more linear, the better. Mario is a linear challenge based platformer at heart, and that's the way his core games should always be. Zelda and Metroid were made varying degrees more open specifically to counter balance Mario's linearity. If you wanted a somewhat less linear semi-open world platformer, you played Metroid. If you wanted fully open world game purely about exploration with no platforming, you played Zelda. Mario is one extreme, Zelda was the other, and Metroid was made to bridge the gap. Don't mess with the trifecta, if you ask me.

With a few rare exceptions, you'll get no argumernt from me there.

I know "linearity" has become a dirty word these days, but most of the time it's the best way to structure a game for a well paced experience, if you ask me. Open worlds usually lead to messy layouts and long, boring traversal.

I reckon I'm in the minority here though.

3D World is a perfect game for the Wii U. I don't think either one would have sold like it. Plus that 3D World is 4 players and that's something that neither of those games can claim. My only complaint is that you can't get the fifth character from the start.

Mario 64. Old school fans would want it because it is the best Mario game, and new gamers would get it because it is Mario.

Galaxy 3 gets my vote. The Galaxy series brought amazing new platforming concepts to the genre.

I mean, I don't agree that it's the best way to structure a game most of the time, at least in world design. Mario, to me, is an exeption though, because Mario was never meant to be a game about exploring a world. To me, it's like asking for an open world Mega Man. You play Mario to complete platforming challenges, just like you play Tetris to complete puzzle challenges, Mario Kart to complete racing challenges, or Smash Bros to complete battle challenges.

But when your game is based on traversing a world to any extent, I think open world is the natural progression to go. That doesn't necessarily mean open progression, though. Games like Final Fantasy and Pokemon are examples that would benefit from an open world, linear progression format.

Aside from examples like Uncharted which are structured to be paced like scenes in a movie, I struggle to think of many games where you're traversing a real world, yet the game isn't worse off for being linear in world design. And even then, I think that those should at least be open area, or little pockets of large open that connect to make a cohesive narrative.

A Mario 64 sequel would most likely sell the most, since a Galaxy 3 would probably sell less than Galaxy 2!