Wow, I was in middle school when this came out. Shadow, and Sonic, are my favorite characters, and when I heard Shadow was getting his own game, I was excited... But then the game came out (-__-)
For me this, besides Sonic Boom, is the worst Sonic game made. I had more fun with Sonic 06 than Shadow the Hedgehog. I feel as though the Gunplay was just unnecessary. The driving was clunky, and it didn't get any better in Sonic 06. In SA2, and to some extent Sonic Heroes, shows Shadow is just as powerful and fast as Sonic. Then you have to beat the game 10 times, to get the true ending, that's way too much than it should be. Why couldn't Sonic, Rogue, or Amy, sat down and told him about his past, and save him the trouble?
As much as I want to erase this game out my memory, it did get some good design choices. When you get hit, you don't lose all your rings at once. They didn't map everything to one button like they did in Sonic Heroes.
If for whatever reason, Sonic Team decides to make a sequel to Shadow the Hedgehog, just make it play like Sonic Generations with a better story than what Shadow the hedgehog had.
Johnny made a really good review, and I highly suggest it, that sums up my thoughts perfectly:
https://www.youtube.com/watch?v=vGPv3fhBWRY