I assume you mean football, basketball, and hockey.
IMO the easiest way to determine the "commonness " or "rarity " of an autograph is to check price guides. The cheaper the autograph the more common . PSA autograph facts is one of the easiest price guides available whether or not you agree with the values they list for autographs.
Also books like Ron Keurajian"s dealing with baseball HOFers can give you a very good idea of availability as well. He even gives a rudimentary breakdown of availability on the type of medium the autograph is on.
I'm not aware of complete price guides on football, basketball, and hockey as there are on baseball.
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