Couple interesting things of note -- Older players from the "golden era" of baseball are on the list for overrated, while the underrated players tend to be more recent. I think media surrounding baseball tends to be blinded by the history into undervaluing the present. Hence the values of historical importance of the game today frequently being lost on the public.
And on Goose Gossage - IMO So many people talk about how underrated he is that he's not really underrated anymore. I know about the HOF junk, though, but still.