Don't believe me? Capcom released a series of comparison images on the game's official site. Obviously, the better looking ones are for the PS3 version.
The HD version of Okami will be out this fall and will feature PlayStation Move support as well as Trophies.
The game's trailer (viewable here) also had image comparisons between the PS2 and the PS3 version. These screens really help drive the point home: Okami should look stunning in HD.