lol, this is exactly what I came in here to say

I thought 2D Mario was made in a day when there was a lot less gaming diversity.

The answer is: Nostalgia

It's simply easier to navigate in only two directions (really primarily one -- go forward) in the 2D Mario games.

3D which allows one to go in any direction is more difficult. You can get lost for one. 

It's the same reason Mario will always be more popular than Zelda ... it's far easier to play. People like straight forward action (running/jumping/stomping) over exploration based titles. Another reason why Metroid Prime with its emphasis on exploration will never be as popular as Call of Duty (blow everything up). 

Though 3D World pretty much brings much of the experience of 2D Mario into 3D almost perfectly. It's probably too bad that 3D World is tethered to a dud of a console though. 3D World on the Wii probably would've sold 15-25million copies (more than either Galaxy game) with its multiplayer + tighter level design. 

That was a good read.

I like both but tend to side with 2d, although 3d world is doing a great job of changing my mind. For me, and i dont know how many other people have this issue, is that i tend to have difficulty asessing certain jumps in 3d mario games, and it can lead to some frustrating levels and cheap deaths.

Also because lots of gamers that fit into the 3D mario player profile only buy non-nintendo consoles.

In "Nintendo should go third party" threads you won't see people that want to play 2D Mario. They want 3D Mario.

Dude making gaming generalizations based on this forum is anti-vgc we use numbers here and they do not reflect vgc opinions. 

2D Mario may be more difficult, or rather, have more points of peril (great read btw), but it is also fundamentally simpler.

The rules in 2D Mario are always the same; 'go right, reach the end'.

In 3D Mario the rules are more complicated, you have to explore, you have to collect, you have to defeat bosses, you have to reach the end.

In short: 2D Mario is simple, but hard, 3D Mario is easy, but complex.

I think it is the complexity of 3D Mario that puts people off, rather than the difficulty of 2D Mario attracting them. I think that the lack of difficulty in 3D Mario is Nintendo trying to ease people into the more complex ruleset. Hence why 3D Land and World, take more cues from 2D Mario than 3D Mario.

*Clapping gif* Someone gets it. I prefer 2D Mario myself, the controls and precision is as good as it gets. The attentiveness required of the player is also much higher than i have experienced in 3D Mario. To be honest, i haven't played as much 3D Mario's to completion.

Mario 64 & Sunshine were simply not for me when i eventually tried both of them much later than their release dates. Galaxy games seem more kind but they took a more linear and focused approach in those games to appeal and convert the 2D Mario gamers to 3D.

I want instructional video for 2D Mario because New Super Luigi U kicked my ass. I'll get back to it eventually.