Michigan has the most participants in football and Basketball. Michigan could have won the championship in football if the OhiostateBuckeyes didn't cheat in the rose bowl.
Soccer.
The UK sport with the most participants is angling
the answer to your question on the most registered playered sport is korfball.
Michigan
Hockey, In Canada of course!
cricket!?!?!?!?!? Fishing has the most participants.
Michigan.
Swimming, Soccer, AFL and Netball
Michigan
Football, i.e. soccer. Football has the most participants and is the most watched.
Contrary to popular belief, the sport with the most participants is swimming. The most popular in terms of viewers is rugby union.
Rugby is the largest played and most popular organised sport in NZ but golf and fishing have more participants.