These 2 save files allow you to start a "New Game Plus" playthrough of Spider-Man 3, since the game doesn't have an actual NG+ mode. One is for a normal playthrough of the game where Spider-Man switches between suits, the other is for a playthrough done entirely as Black-Suit Spider-Man.
Pick whichever one you want, then place it in the game's Save folder:
and rename it to "main_save_data", replacing the existing file (or back up the existing file), then run the game. It will start at the beginning, either with the normal suit, or the black suit, depending on which variant you picked.