Not a disaster, but not spectacular either. ALMOST "Sonic Adventure 3", but not quite.
The Sonic Adventure- style gameplay has been almost completely restored after the exceptionally-loose gameplay of Shadow the Hedgehog, along with the return of the "map world" concept unused since Sonic Adventure 1. The usual run and attack has been restored, with some new styles and attacks within existing and new characters. However, with as many additions that have been added, there is also a negative point. Sonic and Shadow now have trouble reaching the high speeds they are usually known for without boost tracks. Tails is very oddly and unforgivably slow, and his "bomb style" attacks are very difficult to aim and hit. Knuckles and Rouge are practically incomplete, being nearly impossible to dislodge themselves from a wall they have climbed. The errors continue unfortunately, further diminishing the game's rating. The new "ESP" style brought on by new character "Silver the hedgehog" is both innovating and troublesome, often being unpredictable while moving. Although only 3 Hedgehogs are selectable characters, each has 2 additional characters you control at one point or another through their respective stories. Sound is once again a mixed issue. The game's stage music is beautiful and somewhat hypnotic, from the calm music of the map world to the hyper pulsepounding music of Crisis city. Unfortunately, the vocal themes do not reflect the game very well, even more considerably than previous titles.. Sega choose to outsource with several different artists, with considerably poor results (save for "Dreams of an Absolution") ranging from the unbearable "His world" to the (slightly) remixed "All hail Shadow". Unfortunately, Sega has stayed true to their decision with using the Sonic-X based 4kids voice actors since Shadow the hedgehog, none of which do the characters justice. They are truly painful to listen to and beg for the mute button.
Graphics is one of the game's strong points. Sonic Team pulled out all the stops in making the game seem realistic as possible, heavily overhauling aspects such as Robotnik/Eggman's appearance, changing the previously comical robots to more serious automations and putting heavy detail to the human characters. There are oddities however, such as Sonic's form while running at "max speed", the strangely "robot-y" Omega and the somewhat spastic Amy Rose, although these can be overlooked in the big picture. The level design is typical to the 3D Sonic games, although they are more detailed and no longer subjected to the "popup" suffered in previous titles. The cutscenes are beautiful, displaying Sonic and company in a more realistic atmosphere, as wel as replicating the human form well.
The game appears relatively incomplete and shows a lack of effort towards finishing touches, although several updates and downloads have been released since the game's initial release, such as "Team Amigo" and hard mode for each character. While the game is far from perfect, revolutionary or downright great, it's far from horrible and worth an addition to the Sonic Adventure titles.