Actually, the opposite is true. Over large samples, close games for almost all teams, hover right around .500. What the really good teams do, that the terrible teams don't, is they blow people out. They win 5-0, they win 8-2 way more often than the terrible teams do. To use a current example: Baltimore has the single best record in one run games in the history of baseball this year. Would you call them a dominant team?