That'd be pretty ridiculous for a PS3 game to only have 1 save slot. The only games I have seen in modern times that restrict the number of saves, with the exception of Zelda, which does it for nostalgic reasons, are on cartridge based platforms.
Oh, and Xenoblade Chronicles. But that's on a half-assed platform to begin with. The PS3 has a system-standard save menu, which allows multiple save files.