Sonic 4 Part 1: Finished! No, didn't get all Chaos Emeralds. I may be unlazy about this and just keep playing Splash Hill Zone repeatedly until I do, but for now, yeah.
Game's about what you expect from a 2D Sonic Game...with the addition of Homing Attack for some added variety, which is cool. I will say I really don't get the claim that someone made that "The isn't sure if its 2D or 3D." Um, no, its very clearly 2D; I can't even think of a moment where it went 2.5D. It says something that Classic Stages in Sonic Generations are more bipolar than this game (Classic Sonic stages are clearly 2.5D, given they play like 2D, but at times the camera shifts at angles to make things look cooler. Sonic 4 doesn't even do that much.) The only 3D aspect added in was Homing Attack, which actually was a GOOD thing because of what I said before. Well, it also had Triangle Jumping when you don't have anything to home in on...which again, good thing, its a way to make jumping horizontally much faster, as an escape method vs. Boss attacks and such (Sonic's Jump goes way too high vertically and you don't get horizontal fast enough by itself, Triangle Jumping is an extra fail safe that helps.) Took me long enough to finish this but yeah.
Sonic CD: Beat this too! I really don't get the claims of the game having really poor stage design outside of Metallic Mayhem (which is basically Metropolis Zone meets Scrap Brain Zone meets Ambitions Too High To Reach Conceivably. As you'd expect, its a nightmare.) Stages were short, and most promoted "move really fast" (and Starlight Highway is like a precursor to some of the more fun 3D Stages in how its set up!), and honestly there was nothing that stood out about this game, negatively, relative to Sonic 1 or Sonic 2. I guess stages looked pretty boring; first bunch are just clones of stages from Sonic 1/2, last bunch are Cyberpunk Nightmare style stages. I'm fine with how Metal Sonic was the only reference Generations gave to Sonic CD, because that is easily the most memorable thing about the game, as nothing else in that era really has anything comparable to that fight, stylistically.
Game is...also what you;d expect from a 2D Sonic Game! Nice that the XBLA version has Tails as unlockable and he functions like his Sonic 3 self (yay flight!), so its not completely lazy. Not nice how the game doesn't let you replay stages you've already beaten...