Men's swimming events at this year's Olympics: 17
- 100m backstroke Men
- 100m breaststroke Men
- 100m butterfly Men
- 100m freestyle Men
- 1500m freestyle Men
- 200m backstroke Men
- 200m breaststroke Men
- 200m butterfly Men
- 200m freestyle Men
- 200m individual medley Men
- 400m freestyle Men
- 400m individual medley Men
- 4x100m freestyle relay Men
- 4x100m medley relay Men
- 4x200m freestyle relay Men
- 50m freestyle Men
- marathon 10km Men
Men's athletics events at this year's Olympics: 24
- 10000m Men
- triple jump Men
- 100m Men
- 110m hurdles Men
- 1500m Men
- 200m Men
- 20km walk Men
- 3000m steeplechase Men
- 400m Men
- 400m hurdles Men
- 4x100m relay Men
- 4x400m relay Men
- 5000m Men
- 50km walk Men
- 800m Men
- decathlon Men
- discus throw Men
- hammer throw Men
- high jump Men
- javelin throw Men
- long jump Men
- marathon Men
- pole vault Men
- shot put Men
In swimming, you can break the events down by stroke. There's your freestyle, your breaststroke, your back stroke and your butterfly. There is also a total of three relay races where you depend on teammates. Then there are the various distances (50M, 100M, 400M, 1500M, 10KM). That leaves 14 individual events.
In athletics (that title kind of bugs me a bit; don't most events at the Olympics involve athletics?), there are your basic running events and then everything else. To the latter category you can add the jumping events, the pole vault, the javelin/hammer/shot put/discus throws, and the decathlon. There are also two relay events. That leaves 12 individual running events if you include the walking events, the hurdles and the steeplechase.
To me, it seems there would be a greater difference in skill set for Usain Bolt to be competitive in running events and the walking/hurdles/steeplechase than there would be for Michael Phelps to be competitive in four different strokes at various distances. Note that in this year's Olympics, Phelps competed in only 5 individual events (400M medley, 200M freestyle, 200M butterfly, 200M medley and 100M butterfly).