IMO -- Sonic never has worked really as 3D platformer. But that's OK.

Throughout the years, Sega has had some ambitions to make a 3D Sonic game that could stand toe to toe with Mario 3D games in terms of content and popularity, and they've never quite succeeded. 

Sega should take a lesson from Nintendo instead of trying to create a 3D Sonic game franchise to compete with likes of 3D Mario games.

Here's the lesson to be learned: Sega should make a new 2D Sonic game series similar to how Nintendo made the New Super Mario Bros.

Ninty's most popular line Mario platformer games is the New Super Mario Bros series. They're not as innovative, creative, or even as good as many 3D mario games. But they're still really good because they're straightforward and reliably good fun. And that diagnoses the problem I and many others have had with Sonic games. Many Sonic games attempt to be innovative or creative, but they're just not good. The lack focus, and they're just not ... fun.

A return to 2D for Sonic is long overdue. And not half-way attempt like we had with Generations. Full 2D like NSMB.

Its never really worked in 2D either imo...

Sonic 4 wasn't all that great, however. Though one could blame that on the Dimps style of over-emphasizing speed.

Making it too much about the speed is everyone's problem, one that Sega started to address with Sonic Generations and Sonic Lost World, where the 3D sections gave the player more control (indeed, full control in Lost World), compared to the auto-run of the Wii games and Unleashed.

Lost World's problem was mostly in a wall-banging level design (and a few weird gameplay decisions that they scrapped in the first patch). With less of a guessing-game style of difficulty, it could have been received better still.

Sonic 3 w/Sonic and Knuckles ruled. Make something like that, and I would play Sonic again. Sonic has been in a toilet for awhile... Please save him Sega. He can't breath under water...

But they should make it like Sonic 3 & Knuckles! That game was the boobz, man!

This.

I wish they just stopped with Sonic and speant some time with all their great franchises that they love to ignore, Sega can and should be so much more than just the guys that make Sonic to us here in the west.