Sly Cooper is definitely one of the best plat formers ever made for the Playstation 2. This game has excellent graphics, great sound effects and music, and upbeat voice acting. The other good plat formers for the PS2 are Pac-Man World 2 and Jak and Daxter (even though I haven't played it yet).
In the storyline for this game, Sly receives the Thievius Raccoonus, a book written over generations by members of the Cooper thief clan, from his father on his eighth birthday. But the Fiendish Five, a gang of ruthless criminals led by the mysterious cyborg owl Clockwerk, kill Mr. Cooper, steal the Thievius Raccoonus, and rip it into 5 sections of pages. Sly then lives in an orphanage for 10 years, where he befriends tech genius turtle Bentley, and and cowardly hippo Murray. Together, they work to get back the Thievius Raccoonus and destroy the Fiendish Five. There is also Carmelita Fox, an attractive police chief hell-bent on capturing Sly.
The game has a lot of fun sub-games like the one where you move a gun and shoot enemies to help Murray make a run for the key, and one where you participate in races in order to get the key. My favorite sub-game is where I move Carmelita's gun in order to shoot away lava slugs in order to make Sly retrieve his cane. They are absolutely fun and entertaining.
There are also a lot of unlockable Sly movies, e.g. when you get all of the pages of the Thievius Raccoonus, it shows that Sly is now a master thief. My favorite unlockable is the Japanese version of the first Sly Cooper movie, because the animation and art style is far more refined and smoother than the original English movie, and the Japanese speech sounds a lot better than the English speech.
By far, Sly Cooper is THE definitive plat former for the PS2, and I can't wait for the sequel, where you would pick from Sly, Murray, or Bentley. I give this game a 10/10.