There was a major drop in quality though after you beat the main levels and had a series of 5 unnecessary boss battles. They seemed to keep getting worse and worse, until the final boss which was one of the worst and most unintuitive boss battles I have had the misfortune of playing. It was glitchy as hell, and if it wasn't for the walkthrough I read online, I would have never figured it out.This felt more like the 3d Sonic we all knew and hated. But the first 80 percent of the game is amazing. If you quit playing after you beat the main levels (and maybe play the challenge levels also) this is one hell of a game. I have no clue how the hell those terrible boss battles at the end made the final cut though.
Just got this yesterday, and so far i'm absolutely loving it! This is by far the best looking Sonic game in the series, the sheer amount of detail is distracting at times, the gameplay is very solid, the switch between classic and modern Sonic feels natural, the challenges are pretty fun, though some are awfully tough(the racing ones take a bit practice to master)I'm still getting used to the new voice cast though, I honestly prefer the 4kids VA's to the newer ones. So far i'm up to Speed Highway(best level in the game by far), I can't wait to see what's next!