Cowboy was never a top contender. Minor Contender once sure, but nobody thought he could win and defend the thing. He always choked in important matches. He's Dan Marino without the flashy stats. Good in the regular season, choked in the big games.
That being said, he is a fighters fighter, who loves fighting and fights as often as he can and could often get performance of the night bonuses. But calling him a gatekeeper is pretty accurate. Gatekeeper usually refers to someone who can beat 90% of his division, but not the elites. thus they become "that guy" who up and coming fighters test themselves on to get into the title picture.
That is Cerrone to a T