Shadow the Hedgehog is more like Jak 2 or Jak 3 then a Sonic game. In a normal Sonic game, most of your time is spent running around collecting rings and avoiding danger. In Shadow, most of your time is spent picking up guns 10x bigger then yourself and shooting enemies to dust while deactivating/activating switchs and killing a certain number of enemies while flying on a soucer or riding a jeap. In every mission, there are three ways to complete it. Theres the dark way to complete it, the good way and the normal way which ussualy concides you to pick up the chaos emerald at the goal. The pace at which you play is slightly slowler, sense most of your time you will be fighting instead of running.
The graphics within the cutscense are the best I've seen in a Sonic game. The in-game graphics are great, deffiantly top-notch, again, for a SONIC game.
The sound is also good. Instead of your usual Sonic music, the music is more rock. It suits the dark tone of the game, though.
There are five ways to beat the game, which gives it some major replay value. There is also a multiplayer, which lets you play with against Shadow androids of diffrent color schemes.
If you are looking for a nice change from the normal everyday Sonic game, then pick up a copy of Shadow the Hedgehog