This is not a great sonic game but I'd say it's overall pretty damn good. It's an enormous step up in every way from the first episode and deserves its praise.

The physics still aren't perfect but they're at least fun to control now. Biggest mistake is that you don't gain speed while rolling down slopes. I tested it, you can go the same distance while spindashing down a slope and when you spindash up it. You also can still walk-up walls while moving at a low speed but that could also be seen as a bit of convenience so it's not the biggest issue. The spindash itself is quite weak. There isn't that much difference between quick-tapping it to instantly spindash and fully charging it up, both in how fast it is and how far you go. You will legit go FASTER if you airdash in the air and then start running on the ground again which is kinda dumb. Still, even with these problems, it feels 100% better than what was in episode 1 and is still more fun than a standard platformer without momentum physics.

Unlike the first episode which I almost entirely hated, there were only a few things that I'd say are bad in this game. The second boss fight is annoying with how it keeps sending you into the backround so you can't hit the boss, extending the fight. The second act of White Park is cool and unique, but honestly feels more barren than other levels and shorter with you just running. The Sandopolis-like sand rising bits in the last act of Oil Desert can be frustrating if you don't execute them perfectly. There is a Sky Chase zone call back in the first act of Sky Fortress, and while I would genuinely say it's probably the best Sky Chase level in the series, it's still just lesser gameplay compared to the main game.
I wanna point out how cool I think the special stages are. They're the half pipe again but I think this may be one of the best versions of it. I do recommend trying to get all the emeralds as the special stages are sorta fun. The last one is quite hard though. Pro tip: If you lose the special stage you cannot return to it after being kicked out. You'll have to collect 50 rings and jump into the big ring at the end of the level again. For some reason though you can just retry the special stages at any point while playing them, not even at a cost to your stock of lives I'm pretty sure.

One of my biggest gripes with this game is how you're forced to play alongside Tails and use combo abilities with him. I wish I could just play as Sonic and not have to sit through the game pausing for a second every time it makes me use one of these moves. When it comes to the longer Tails flying sections, these again are just lesser segments of gameplay that I can certainly get through but would rather just skip. Also, it's real annoying that performing one of these moves takes you out of your super form. You'll have to waste time watching the animation of you turning super again every time you need to use Tails. This is honestly a more subjective opinion that some people may or may not have a problem with.

The visuals and zone themes in this game are certainly better. The first zone though is on the same tier of originality when it comes to the first episode's zones, legit just being Aquatic Ruin zone from Sonic 2. Every other zone is stuff that has been done before in the series but they're not just taking directly from old zones, instead being actually new locations. White Park especially I'll applaud for being unique because there weren't any amusement park zones with roller coaster tracks in the classic games ( Unless you count Sunset Park from Sonic Triple Trouble which is an abandoned amusement park I guess. ) The visuals of this game are notably much better, actually being 3D modeled now and getting rid of that plasticky filter.
The music is styled the same as the first game. I like more tracks in this game though, especially Oil Desert 1, White Park 1 and Death Egg MK 1. I still absolutely hate the shakers that are used throughout the entire ost. They hurt my head and stuff, too intrusive and repetitive. I'm not sure if many other people can relate to me on this though.
 
Honestly, if this episode started off the series and it wasn't called sonic 4, I'd say that it would've been a good series that people would look back fondly on. It's honestly sad that the third episode was cut as I'm sure the improvements made there would've been even better. If you're a sonic fan then I definitely would recommend this game if you're interested in playing lesser sonic media. If you're not a sonic fan then you should go play some of the original classic games first and then come back to this if you're interested. Do NOT play the first episode though...

Its fun graphics are great! But for touch pad please change the controls to the same ones from episode 1 :(

the game coems with a error: When the game will start, the config files is not available, so the game crashes. I found on internet, the files, to put on folder BEFORE you start the game, now works fine

Great game, good graphics, funny as always