Sonic 1 and 2 recently, so let's take a look at what I'm pretty sure was Sonic's last game on the Genesis, Sonic 3D Blast. I was pretty amped when this came out, I mean Sonic in 3D? Back then this seemed pretty bad ass. The game isn't a true 3D, as this was just the Genesis, but rather uses an isometric perspective to give the illusion of 3D. In the game you have to rescue little magic birds called flickies that Robotnik has turned into robots because that's kinda his thing. You can only complete each part of the stage once you found all the birds. Neither Knuckles nor Tails are playable in the game but rather are hidden in certain spots and will take you to a special stage to get a Chaos Emerald if you have 50 rings. The special stages are easy as hell but getting all the emeralds doesn't give you Super Sonic.
A lot of people didn't like this game and I can see why. The controls are awkward and the game just feels slow and at times tedious. I don't think it's as bad as Sonic Spinball, which I think is virtually unplayable after the second level, but it does feel like a chore at times. I liked it a lot when it first came out, but that was mostly from the novelty of playing as Sonic in 3D, or at least as close to it as the Genesis could muster. This isn't an awful game, and is maybe crapped on a little too much, but it's not very good either. I could only recommend this to a hardcore Sonic fan.