Whoso pretends that Love is no great god,
The lord and master of all deities,
Is either dull of soul, or, dead to beauty,
Knows not the greatest god that governs men.
 
[Ἔρωτα δ᾿ ὅστις μὴ θεὸν κρίνει μέγαν
καὶ τῶν ἁπάντων δαιμόνων ὑπέρτατον,
ἢ σκαιός ἐστιν ἢ καλῶν ἄπειρος ὢν
οὐκ οἶδε τὸν μέγιστον ἀνθρώποις θεόν.]

Euripides (485?-406? BC) Greek tragic dramatist

Auge [Αὐγῃ], frag. 269 (c. 408 BC) [tr. Symonds (1880)]
    (Source)

The second line ("καὶ ... ὑπέρτατον" = "the highest of all deities") was apparently inserted by Stobaeus.

Nauck (TGF) frag. 269, Barnes frag. 15, Musgrave frag. 3. (Source (Greek)). Alternate translations:

He who esteems not Love a mighty God,
And to all other Deities superior,
Devoid of reason, or to beauty blind,
Knows not the ruler of this nether world.
[tr. Wodhall (1809)]

Anyone who does not count Love a great god,
and the highest of all the divine powers,
is either obtuse or, lacking experience in his benefits,
is unacquainted with human beings’ greatest god.
[tr. Collard / Cropp (2008); Funke (2013)]

Whoever does not judge Love to be a great god, and highest of all the divine powers, is either a fool or, lacking experience of his good things, is not acquainted with mankind's greatest god.
[tr. Wright (2017)]

Whoever does not think Eros a great god
is either silly or ignorant of blessings.
[Source]