You can restore the PS3 in the Settings menu but this does not revert the firmware back to the initial version- it's at the latest for good.
One would think it would affect all games if it is a firmware issue, not just the Sony- published exclusives. For that reason I'm thinking it may be the games themselves or the save data for them. You may want to try deleting the data for these games and start fresh, both in the save data and the game data folders. If that doesn't fix anything time to call Sony tech support.