Well, there's not just one answer. And a complete answer would be very difficult to determine.
Look at the recent teaser movie for the new Pump version posted here in another thread. On the credits screen at the end of it, you will see about a dozen names under "Step Creators." And those are just the stepmakers of the NEW songs in that version. That's not counting all the old songs carried over into the new version, which would include even more stepmakers.
It's common to have many stepmakers. It's a difficult process to create good steps, and takes alot of time. They take great pains in doing so, trying to keep the step charts at a high level of quality and playability.
Logically, Freestylers generally create Freestyle steps. Elite Speeders generally create the Crazy and Nightmares.
Regarding Exceed 2, you could cite Overdeath as one of the stepmakers for that version (Freestyle stepmaker, primarily), among many others.
And if you come to USPF2007 next weekend in Chicago (see other thread here), you can meet Overdeath there. Here is one of his famous old Freestyle vids, just recently posted on youtube:
YouTube - Overdeath's "Mistake" AKA "Guilty Conscience" Team Freestyle