Baseball fans of the 1960's and 70's recognize no peer to Johnny Bench, the acknowledged leader of Cincinnati's Big Red Machine. A major home run threat with a powerful throwing arm, he was also considered an excellent handler of pitchers. The still active Mike Piazza has many supporters on the basis of his career batting average above .300, far above Bench's .267, and a record for catchers of over 400 home runs.
In the 1930's, however, the debate was Mickey Cochrane of the Philadelphia Athletics and later World Series-winning player-manager of the Detroit Tigers versus Bill Dickey of a New York Yankees dynasty. Both had lifetime batting averages well above .300, but were particularly esteemed for their fielding and signal calling.
Going further back to the first two decades of the 20th century, the names of Roger Bresnahan and Ray Schalk stood out. Bresnahan, a stalwart of John McGraw's New York Giants, is credited with designing some of the catcher's equipment that became standard. His batting average was .279, but he, too, was valued for his defensive skills. Schalk, named as the all-time best catcher by no less an authority than Babe Ruth, was in the Bresnahan mold while batting only .253.
The ideal catcher helps his team with the bat and behind the bat. Hitting is fairly easy to evaluate.
Unfortunately, fielding statistics tell very little of the catchers' contributions when the opposing team is up. The standard computations of assists, putouts, and errors depend greatly on the talents of the teams' pitchers; for example, how many batters they are allowing on base and how close to base they are holding runners. Piazza's fielding percentage of .991 is higher than Bench's .987, but few would put the former in the latter's defensive class.
The evaluation of catchers' defensive contributions is therefore uniquely subjective. Arguably, their most important role is their interaction with pitchers, including pitch calling, advising, and calming, as well as tipping the manager when the hurler is becoming ineffective. These activities defy quantitative rating, but sophisticated observers can appreciate excellence in their performance.
Consider two other "all-time" candidates. Yogi Berra came up with the Yankees in 1947 with a reputation as a natural slugger but with much to learn as a catcher. After two seasons in which he proved both points, he was assigned to the tutelage of Dickey, who had become a Yankee coach. Berra gradually became a fine defensive catcher. When he received his third Most Valuable Player award in 1955, he had batted only .272 but had gained respect for the smooth handling of a pitching staff that no longer had the unbeatable Reynolds-Raschi-Lopat combination of the early 50's.
A contemporary of Berra's, Brooklyn Dodger Roy Campanella, set the record for home runs by a catcher at 41 and was considered Berra's superior defensively. Also a three-time Most Valuable Player, Campanella got a late start because of the color line and is sometimes overlooked because he played only 10 seasons.
A final complication in rating catching greats is what to do about Josh Gibson. In a career entirely in the Negro Leagues, he is credited with approximately 800 home runs over 17 years as well as ideal skills behind the plate. Gibson died in his mid-30's months before Jackie Robinson broke the major league color line.
Reference: Baseball-Reference.com