It's not what's great that is good, but what's good that is great.

Δημοσθένης ὁ ῥήτωρ θεασάμενός τινα δημαγωγὸν ἀφυῆ μέγα βοῶντα ἔφη 'ἀλλ᾿ οὐ τὸ μέγα εὖ ἐστι, τὸ δὲ εὖ μέγα'. | Demosthenes the orator, seeing an inept demagogue shouting loudly, said: It's not what's great that is good, but what's good that is great. | Elsewhere attributed to the aulete Caphisias (Athenaeus 629b, Diogenes Laertius VII.21). | The most widely circulated paraphrase is first found in Proverbs; or, the Manual of Wisdom (Oxford, 1803), p. 118 | Every thing great is not always good, but all good things are great.