In my mind, there’s a difference between a good pitcher and an ace.
A good pitcher is someone you want on the mound. When you’re scanning the upcoming pitching probables, he’s a name that you’re happy to see. He’s got a pretty dang good pitch, and a few decent secondaries, he can give you five or six solid innings, and he’ll put you in a good enough spot to win.
But that’s the thing — he’s good, not great.
An ace, now that is a thing to behold. Think King Félix Hernández, taking the mound every five games to his own cheering section.