Plenty of people just bought Wii games early in the cycle based on hype or thinking the box looked neat. 

My cousin who bought the Wii for Wii Fit bought Mario Galaxy because she felt like getting a Mario game, but she didn't know it was as complex as it was (NSMB would've suited her better). 

If the so-called "expanded audience/non-gamer" crowd was as casual as rivisionist historians claim though, they wouldn't have bought a Mario game in the first place, they would only have bought "non-games" like Wii Sports, Just Dance, Zumba Fitness, Wii Fit, etc.

Mario Galaxy had strong core appeal; it was both presentationally and mechanically ambitious, and it was one of the highest reviewed games of all time.

And still given all that it would've sold maybe 5-6 million on the Wii U. 

Mario 3D World is no slouch when it comes to reviews. 

In all honesty, Mario 64, Mario Galaxy, and Mario 3D World have a case as the three best Nintendo games of the last 20 years. Zelda: OoT and MM are probably the only other two that enter into the discussion. 

3D World's reveal was met with a surge of disappointment from gamers who felt it looked lazy and conservative. Even today, many still claim it's not a "real" or "proper" 3D Mario game. I doubt Galaxy 3 would have gotten as much backlash, the series' epic cosmic vistas and more ambitious stage design produce a more flashy, marketable image.

I doubt a third galaxy would have done that well unless they shook up the formula a lot. People would have criticized it as more of the same and it wouldn't have escaped the unfair negative opinions all wii u games were suffering back then. Still, it might have sold a bit better than 3d world.

I'd rather have a Mario 64 successor and I hope there's a market for that kind of exploration orientated Mario game.

Mario 64 is one of the greatest games of all time, for me, and the idea that people believe there isn't a market for games like that, and people just want linear galaxy like experiences, is not only a depressing point of view but it's almost completely untested.

I'm pretty happy with 3d world. It captured most of what I liked about galaxy and had had a great local multiplayer. Now that I've got Smash and Mario kart I still find 3d world is my goto multiplayer game when people come around. It would have been great as the launch game instead of nintendo land, but oh well.

The first trailer was meh but subsequent trailers and final reviews for the game were fantastic.

Mario Galaxy got to sell to a 100 million userbase, it's sales woud've easily been halved (if not moreso) if you cut the Wii userbase to 17-18 million like 3D World has to deal with. 

This is a whole lot of bruhaha over nothing IMO, the second half of 3D World is basically very close to what a Galaxy 3 would be anyway (there are even space levels).  

i think a mario game with the super mario 64 format wouldve done better,that's what people were expecting instead of 3d world

Userbase is no guarantee of sales though; Metroid Prime sold more on 22 million Gamecubes than Other M did on 100 million Wiis. I'd contend Galaxy is simply more marketable to the core gamer than 3D World. But we may just have to agree to disagree.

Probably Galaxy 3, but I dont want Nintendo to make Galaxy 3, two games are more than enuf, but Mario 64 2 in other hand would be great, evan Mario 3D World 2 for me would be better than another Galaxy.

Fans are just waiting for that Galaxy 3 announcement.