This is by far the greatest Sonic game made thus far, created by Sega or otherwise.
This is the peak Sonic experience to date. If the ideal Sonic game could be summed up in one word, it would be "flow," and Sonic GT understands this. The tools at your disposal (two types of homing attacks, bounce, trick flip, drop dash) are perfect for what the game needs to reach that excellent flow state. Sonic's speed is exhilarating, the level of control is amazing even at high speeds, the level design is branching and expansive, environments are beautiful, music is bangin', Sonic is expressive, and the game is an absolute blast to play. I love it so much and I have always wanted a game like Sonic GT. This is the absolute closest anyone has ever come to perfecting the peak Sonic formula. Literally 10/10 from me on all fronts, except for a few criticism listed below.
Of course there are always things to improve upon, so here are my constructive criticisms:
1. The story hahaha. To preface, I don't even care about the story really. For me, it's all about the beautiful physics system and level design, seeing Sonic at his peak during the levels. However, the writing is cheesy, the voice acting is god awful for pretty much every character except Eggman (no offense guys I know you all tried your best but I turned Sonic's voice off during the levels entirely, and this is coming from someone who thinks Sonic's voice in Sega games is hecka rad). Also, Sonic and Shadow do not hate each other. SA2 was pretty much the peak story-telling for Shadow, which solidified Sonic and Shadow as friendly rivals that have a mutual respect for one another. The bastardized characterizations of the Sonic cast from the last decade are awful and I wish this game didn't play into that, but like I said, it's whatever to me because the real selling point of the game are the actual levels, which are amazing.
2. The tutorial does not explain how the trick system works. I figured it out myself, but one thing I still don't understand is: in some levels or challenges, the trick system only rewards you based on your highest trick combo, while in others it adds all trick combos together. Can't seem to figure out why that is. Definitely need to explain that in the tutorial guys.
3. I understand why this next point is sort of necessary, but it still has to be mentioned: I love the fact that the game is non-linear and there are SO many branching pathways to reach the goal. However, every level is so large and the pathways are so numerous that it is almost guaranteed YOU WILL GET LOST first time you play them. Happened to me every single level. I personally don't mind this much because I enjoy routing an optimal path in a level and then finding more optimal paths once I get a sense of the levels direction. It adds so much replay value even after S-ranking all the missions and it's one of the reasons I really love this game. However, while it's not a personal gripe, I don't think people should get lost while playing the level first-time. That being said, I AM NOT in favor of making the levels more linear. With how fast Sonic moves, you NEED very large expansive levels in order to have branching pathways that actually make a significant difference in how you finish the level.
I believe the best fix for something like this are more indicator signs throughout the level (like how Sunset Boulevard has arrows that show the direction you should go). It shouldn't be too hand-holdy, but they should just give a general direction of where to go. More of those sprinkled in every level and this is entirely a non-issue.
4. This next point definitely has to be corrected I think: the trick system can be manipulated to easily grind points. By spamming bounce with every landing or by staying on the ground for a very short period of time (like .5 of a second), the trick counter will stay indefinitely. As I see it, the trick counter should work to reward you for doing cool stuff *while maintaining speed and flow*. However, seeing as how you can basically keep the counter the whole level just by bouncing and quickly hopping off the ground when you touch it, it rewards a slower and more grindy type of gameplay. By using these exploits, it actually *discourages* running and keeping a speedy flow. Definite fix needed there in my opinion.
5. Enemies and springs are hard to see from even a moderate distance. I know the map has to be huge to account for Sonic's speed, and making the enemy sizes and springs giant wouldn't really make sense in proportion to Sonic, so I'm not sure how to really fix this one. It may be inherent to the design of the game. Not a big issue, but worth noting.
6. I think it was the intention, but Hidden Base is TOO DARK and I hate it lol. Same goes for the shady areas of Hill Top. Granted, I do have a blue light filter on my screen which makes it harder to see dark areas, but it shouldn't be to the point of complete blackness, especially in an otherwise bright area like Hill Top. I'd definitely make these areas a little brighter.
7. The inclusion of the old Fire, Lightning, and Bubble shields are awesome. However, it is annoying how the shields replace your Right button command. I mostly play Sonic, and I feel like the drop dash serves as an integral aspect to maintaining the flow of the game, it doesn't feel right to not have it. So I find that once I actually get a Fire, Lightning, or Bubble shield, I immediately want to throw it out, because I would rather have the drop dash than the shield ability. I would definitely change this and move the shield ability to the Right trigger rather than the Right button. Right trigger is a completely unused button and that way we would not have to forfeit the drop dash or other character abilities when wearing a shield.
8. The bosses are literally better than any boss Sega has concocted in the last 20 years lol. However, the Eggman Tank and the boss at Hill Top still follow a similar formula, which is: wait till you can hit them. Hill Top's boss less-so because you can get in multiple hits every time he comes off the rail, but still speeds up to the point where you basically have to wait until you are both on the ground again. And also (I'm not sure if this was intentional or not), you can't hit the Hill Top boss while he is on rails, because the homing attack auto-targets the rails and never the boss. Still great bosses, but just prefer something with less "wait till you can hit them" approach.
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Aaand that's all I got. Besides these relatively minor and very fixable criticisms, I think you got THE PERFECT FORUMLA on your hands here. This is coming close to my favorite game of all time and the only reason it's not my favorite game of all time is because it's only 4 levels long and because of some of the criticisms mentioned above. I've always wanted a game like this. The closest we ever got to peak Sonic experience before this was Spark the Electric Jester 2, which is I also really love, but Sonic GT's sense of flow, immaculate control, and creativity in level design actually beat out Spark's IMO. Big respect to everyone involved. I love what the team has done and am excited for any future projects, updates, or expansions.