Even Babe Ruth wasn't a unanimous selection. Rickey is the all time leader in stolen bases and runs, and is second in walks to this guy. A look at his career stats should leave you in awe. If not, remember that when he broke Lou Brock's record for career stolen bases he uttered this gem:
Lou Brock was the symbol of great base stealing. But today, I’m the greatest of all time.
He has a personality all his own, and that may have cost him a few votes here and there. Ultimately though, he'll go down as one of the best ever, and in terms of getting on base and being a threat to score from anywhere, he is unmatched.