Player's Fault
As for the game itself. The story is a bit too short for my taste and the endings are all too similar but each path shows a new piece of Shadow's history. Multiple endings probably wasn't the thing SEGA was aiming for, but multiple paths that unlocked Shadow's past. Instead of just making one story SEGA wanted the players to have to have a new experience in order to learn.
Now that I've cleared two things up there is the guns issue. Guns were not useless. Some levels they weren't necassary but in other they helped out a lot. If you don't want to go in and risk losing your life when you're fresh out of rings then fighting with a weapon is your best bet. Even against the giants they help, you shoot to distract and then homing attack. So the guns weren't completely useless and hey, they were easy to use.
As for levels, those were very expansive and fun for me. I was able to explore a little while still getting Shadow's top speed. Though the vehicles in each level were useless unless you didn't feel like getting hit and losing some rings, then wanted to run over some aliens or humen. Oops, I gave it a use didn't I?
In the end if YOU yourself experienced any problems the blame falls on you. Other then some levels that contained seizure giving colors the game was good. I didn't mind the graphics because I had already experienced Sonic Heroes. Besides that the cinematic graphics were great so I couldn't complain. Other problems you may think were in the game were:
-Repetetive Bosses, you fight the same ones over and over.
-Inaccurate homing attack(Try using your analogue if you experience this one. -_-;;)
-In accurate guns(Try facing your target or even jumping...)
-Falling off a cliff after running(Slow down and look around...)
Those are things I've heard from the public but have rarely experienced myself. That's why I don't think the game was bad. I bought the game after I heard all this stuff from people and expeced something horrible but the game was interesting and very good though easy.