Honestly, I can still go back and play this, but not without feeling embarrassed.
If you liked Sonic Heroes, this game plays a lot like it. The controls and graphics are very similar (perhaps even worse). But with that comes the flaws of Sonic Heroes. Rehashed levels, loose controls, and dumbed down level design.
The mission can sometimes range from creative, to downright frustrating gameplay. The worst of them all is when you have to kill all enemies on screen, an old concept of padding out the gameplay that dates back to the Chaotix gameplay on Heroes. It's simply not fun. Going through the levels normally, just trying to get to the end, is when the game is at it's best, and sometimes impressive. But other times I will run into levels where I just want to RUN, but am often stopped looking for something, or am just secluded by the nonlinear and confusing designs of the level. It would've also helped if you couldve chosen the mission you could do in the beginning of the level instead of half way, so people would stop interupting you mid way through the level, and your allies would stop attacking you.
The guns, while dumb in concept, can sometimes be fun to use. When surrounded my hordes of enemies, unleashing your rage by jumping in the air and unloading on your enemies, can sometimes be a satisfying experience. There are some melee weapons included in the game, like a blade, that are also pretty cool to use. But any weapon that doesn't aim automatically its more of a pain to use, and not worth your time.
The vehicles are a different story though, and are usually not fun in the slightest. First of all, why drive when you run twice as fast. Sure, its amusing to see shadow ride in a bike or buggy, but its completely pointless gameplay wise. Other vehicles like the walker make more sense, but could've been replace by the classic spring. In the end, these vehicles are really there to add to the insult more than the fun.
But the thing that really puts the nail in the coffin is how uninspired the endings are, all so similar to eachother, and are all needed to complete the game.
You will hear every time "Finally, I have all 7 Chaos Emerals, I am Shadow the Hedgehog, and I am a good guy", or "I am a bad guy" or, "Im don't know who I AM." Ending. They're all unsatisfying, and are all NOT the real ending. The drive and flow really discourage you from completing the game.
Overall, the flaws of Shadow the hedgehog put it in nearly into the "not worth playing" category. But since it retains the elements that make Sonic good, like the speed and the action, it saves the game from being a total waste. As much as I hate to admit it, I can still go back to this game and say "you know, this isn't to bad." Or maybe it's because Sonic games have gone so downhill I just don't know what is good anymore. Or maybe I have really bad tastes. Well, thats for you to decide.
Final Verdict: This is only for the die hard Sonic fan, or for 10 year olds. The rest should stay away.