Does ace mean really good?

Excuse me, could you clarify something for me? I've come across the term "ace" in a few different contexts, and I'm wondering if it universally means "really good." Is that the case, or does its meaning vary depending on the situation? For example, I've heard it used to describe someone's performance in a game, but also in reference to something like a test score. Is there a consistent interpretation, or does it depend on the context?