The new Ultimate Levels are tied to New Game Plus (as is a new Trophy) and can only be accessed once you’ve beaten the game once and then chosen the New Game Plus option which lets you restart the whole adventure with all of your suits, gadgets and levels intact.
Essentially, Ultimate Levels let you level up past the standard 60 levels in the base game. Chances are, if you’ve beaten the story you’re probably close to or have already gotten to level 60. If that’s the case, you’ll start New Game Plus at Ultimate Level 1.
Each new Ultimate Level will increase Peter and Miles’ base health by a small amount. You won’t unlock any new skill points though, because you’ve already maxed those out anyway.
However, you will unlock some sweet new goodies in the form of brand new suit styles relating to the Black Suit, the Symbiote Suit, and the Anti-Venom Suit. To unlock them all, you’ll need to reach Ultimate Level 9.
That might take some grinding though, because each Ultimate Level takes a hell of a lot of XP. Just going from level 1 to level 2, for example, takes 41,000 XP, so you’re going to hit up every side-mission and activity possible, including aiming for the gold medals wherever you can. The new option to replay main story missions may help with that.
In short, the new suit styles are a visual representation of your devotion to Marvel’s Spider-Man 2, even more so than the Platinum Trophy.