Shadow the Hedgehog starts off on the right foot with a great CG introduction that's slick, cool, fast, fun and entertaining -- everything the actual game isn't, really. The confusion begins as soon as the game starts; you're dropped into an intense battle inside of Megalopolis with Sonic immediately asking for help. Of course, the hook of the game is that it's up to players whether you help Sonic. You can freely choose between working the side of good or evil in each mission, and in order to see all of the game's stages and endings, you actually need to make different decisions when you play through the game.
Unfortunately, the game does nothing to explain this idea of good vs. evil, nor do much to help players take advantage of it. Chances are you'll mistakenly find out you even have a choice by pausing the game. Let's say, for example, you decide to be good. Because you can still actively switch at any time, though, the "good guys" can still hurt you, meaning the game artificially doubles the obstacles in your way for no reason, even if you're on their side. Sonic games have always been about speed, and it's annoying when you're painfully navigating through your "friends" just to move forward.

The lack of speed is a real problem here. The switch to 3D has been a source of great concern to Sonic fans due to Sonic Team's inability to really capture the essence of the 2D games in the free-roaming format. Shadow the Hedgehog doesn't do much to change that. Granted, the areas are much less open than in previous Sonic games, but the level designers haven't taken advantage of the constraints. You're still forced to stop moving every few seconds and mow down enemies to progress; the few moments where Shadow's speeding around, dodging obstacles, and shooting into the sky off of speed ramps are awesome.
The whacked camera angles mean there's less control over these moments compared to the old-school games, but the sheer adrenaline rush is almost enough reason to explore more levels to see if it comes back. There should have been far, far more moments like this in the game, and this literal lack of momentum kills Shadow the Hedgehog's potential. You end up spending more time picking up weapons and fumbling with their aim than the level design. How many times can you remember preferring bopping robotic crabs over speeding through ridiculous loops and jumps in the original Sonic the Hedgehog?