Bill James has Santo as the 6th greatest third baseman of all time. Sosa's ranking at RF is 19th greatest of all time right fielders through 2003, and it's pretty clear that what he did in 2004-2005 did not boost him much. His win shares per year are basically equal to Sosa, and his OPS+ is only 4 points lower than Sosa. When you consider that Santo played a premium defensive position, and played it at a Gold Glove level, while Sosa was no better than average in RF. It's really easy to argue that Santo was better than Sosa. Is it unthinkable that outfielders might be so much better offensively than third basemen that maybe the 19th best RF is still better than the 6th best 3B? Yes, because the stats I gave you above suggest that Santo was just as good offensively as Sosa. If you want to make a direct comparison between third basemen and right fielders, or right fielders and catchers, be my guest. I think it's much more fair to rate a player versus his peers - those who played his position.