Agile is defined as;
"Characterized by quickness, lightness, and ease of movement; nimble."
Nightcrawlers body structure allows him to be more agile than any other contestant. Yes, spidey and beast can do bigger moves in the air, but those are consistantly considered less difficult than transfers and the form of dismounts. (In regards to the bars)
Floor event is characterized not by how big you go (Yes thats important) but also form and style, being able to perform every single maneuver on your hands, and to twist your body in the ways nightcrawler can will give him a good edge here, although beast will also excel in this.
Rings require strength, yes, but nothing nightcrawler doesnt have, and the fact that he can do the rings with his feet will definitly look good.
Balance beam is built for NC and Beast, both can manipulate their limbs with more experience and skill than spidey, who is no slouch here.
The only reason why TM can't beat NC, is because he can't do everything NC can because of the build of his body.