NFL is a shining example of good competitiveness through equaling the markets. Some markets have more resources available to them and would greatly deter competition in the league.
The NBA has a less stringent salary cap implemented. It remains competitive, but mostly through good drafting and lucky ping pong ball bounces. The salary cap deters players from leaving their original markets which is very nice for the fan base.
MLB has no salary cap. The best teams are consistently in the playoffs. The Royals , however, are an exception to the strong markets dominating the field. I would make this argument. If the Royals competed in the East, they wouldn’t make the playoffs.