A similar debate can be created surrounding the term "Number-One Pitcher", but I'm going to hang on to that nugget for another sleepless night.
An Ace, to me, is a starter who can give their team 230+ innings per season, a K/9 rate of around 8.5 or higher, a FIP below 3, and chocolate-vanilla-twist soft serve ice cream from their armpit - home AND away - and can do it on an annual basis. Well, everything except the ice cream. Basically, I don't call a lot of starting pitchers Ace, even if they are the team's top o' the rotation guy. Those guys, I call "Staff Aces",
To me, the waters are so muddy on this subject, I decided I should put together a visual aid to help the average baseball watching person (like myself) determine one type of Ace from another. To help the internetting folks among us, I have captioned them in the easy to recognize Image Macro/Meme font, Impact. Which I like to call "Meme-pact". I don't actually call it that, and neither should anyone.
I hope we all learned something.