If you encounter files claiming to be a "Sonic Unleashed PSP ROM," they are likely one of the following:
This is widely considered the best official way to play. The game utilizes Xbox backward compatibility to fix the severe frame-rate drops that plagued the original 2008 Xbox 360 release. PlayStation 3 Go to product viewer dialog for this item. Go to product viewer dialog for this item. : The original "HD" versions of the game. Wii & PlayStation 2 Go to product viewer dialog for this item. Sonic Unleashed Psp Rom
In short: Every "Sonic Unleashed PSP ROM" is a fan-made port or mod, not an official Sega release. If you encounter files claiming to be a