Bully is a great game that could've been even better had it come out on a better console.
The core gameplay is almost lifted directly from GTA but feels fresh because of the new setting and story. The area you inhabit is considerably smaller than what you'd find in a GTA game but it's definitely appropriate for this title. So basically you have the free-roaming aspects of GTA, the fighting system from the Warriors and the stealth and targeting system from Manhunt... this a Rockstar game through and through. And a damn fun one at that.
The presentation in Bully is solid but hardly awe-inspiring. The graphics are ok for a PS2 game but the audio is pretty great. Appropriately humorous music is heard throughout and the voice acting is terrific. The characters you encounter are all well designed and given loads of personality thanks to the writing and acting. Great stuff.
My only complaints are about the length and difficulty. The missions you take on are varied and fun but can be completed fairly easily. Even the ones toward the end of the game aren't too challenging. The game is also a bit short. About 12 hours worth of gameplay is what most folks will get out of it. In closing, if you're a fan of Rockstar's games this one should be a no-brainer. It's a good time all around.