Too hard to call!
First thought was sanchez, but cos of his shortened career it is always debatable as to how he would have gone had he fought for longer.
Chavez was great but he fought too many bums at the start of his career and fought on too long at the end. Prime, mid career Chavez has claims.
Ricardo Lopez'z record and skill speaks for itself, but cos he fought at such a small weight he is not as well known and may not have had the lvel of competition of the other 2.

I'll go Sanchez, but could easily have voted for Chavez or Lopez.