I got the game tonight (with a few other purchases) and beat it.
That was the best six hour fangasm I've ever had. ;-;
Note: There are spoilers in this topic so be wary of what you read.
I sat there and played that game from beginning to end, including the chaos emeralds and final boss, without stopping for anything.
Let me say this: I was going in expecting remade stages, but what I wasn't expecting was the absolutely amazing creations I was given. Every stage was so...original. Despite the fact they were based on levels from previous games they all still felt like their own levels. They were brilliantly designed and the music for each stage was amazing too.
Oh and don't get me started on boss fights, the first one was far more amazing than I expected it to be and was thoroughly epic, then Perfect Chaos came and though the fight did the same stupid crap that I hated about the original one where they went from the awesome theme song of the game to the not-so-great "final boss theme" everything else about the fight was amazing. Perfect Chaos looked way cooler and the level itself was so much better. I had so much fun running across the ruined buildings and through the water and seeing Perfect Chaos in the background while his water tendrils attacked me from afar. It was a really epic fight.
The final boss itself...well the music wasn't so great but the fight itself was pretty interesting. Had a bit of trouble figuring out what to do (not unusual for me when it comes to Super Sonic final bosses lol) but in the end it turned out great. The friends constantly talking through the communicator was rather useless and annoying though. It wasn't even interesting dialog like in Sonic Adventure 2, it was just "DODGE THIS, SWITCH WITH TRIANGLE" over and over and over. -_-
I've yet to do any of the challenges except for the "Friend Challenges" which I chose to do so I could get the boss keys but it definitely looks like a lot of fun to do them all. The rival fights were definitely great, especially the Shadow rival fight, that one was amazingly well done, especially with the music changing depending on who's in the lead. Now that was a truly epic fight.
My one and only disappointment with the game was my one most anticipated stage: Crisis City. It was fun but it didn't feel like such a jump from the original like all the other stages.
Speed Highway, Chemical Plant and City Escape were definitely my faves and I definitely favor the Modern Sonic stages. This game was absolutely amazing though, it was the best six hours ever.
When I finished City Escape I was like "Now that is how you escape from the city!" cuz that level was just so damn fun.
What got me most in a lot of places was the great use of the scenery to get through the levels. Sonic jumping off of street lamps, an Orca Whale bumping me so I flew farther, etc.
This game made great use of the back and foreground. This is truly the best Sonic game and you'd be a fool to not recognize it's greatness.
Oh and also, this game had the best world hub I've ever seen. It was amazing.
10/10, truly the best Sonic game to date.