Baseball, aka Super Cricket. I guess mainstream society really is turning away from boxing if they don't mention Louis or Johnson.
Joe Louis as others have said did more than any other black athlete in history to bring down the colour bar. He was also the first black athlete to gain general aceptance among the white community. Today after the election of Barack Obama as the first black president, in large part by white America, he is more relevant than ever.
Baseball is the preferred American past time over just about any other sport in our country. Therfore, its no great surprise that an African American athlete would receive greater praise for being the first in this realm over boxing.
It should be noted that one of the commentators on CNN did reference the Louis-Schmeling rematch in addition to Jackie Robinson's breaking the color barrier in baseball, but it seemed the exception rather than the rule.
Nobody ever talks about strides Barbados Joe Walcott made in the early1900's as one of the first and dominant black champions. No disrespect to Jackie Robinson for what he did with regards to the colour barrier in baseball. There were many great negro league players before him that never got the oppurtunity to play in the major leagues.
Jackie Robinson was great in what he did but he was very overrated as a ballplayer. Joe Louis is arguably the greatest Heavyweight of All time and did a lot for the African American community.