Phelps has won the 400 meters individual medley, 4 x 100 freestyle relay, 200 m freestyle, 200 m butterfly, 4x 200 freestyle relay, 200 m individual medley, 100 m butterfly and 4x100 medley relay.

I think swimming freestyle and butterfly are two totally different strokes and must be similar to a runner running 100 meters and 110 meter hurdles.

I guess for Bolt to match Phelps he would need the following.

100 meters
200 meters
110 hurdles
200 hurdles
400 metres
4x100 meters
4x200 meters

Then he'd be better imo.