Why do Greeks love Russia so much?

Greeks (OK, Byzantines) gave the Russians Orthodoxy, and feel a bond with them out of that. During Ottoman rule, the Russians saw themselves as the Third Rome—the successor state to Byzantium, which the Greeks felt was their lost empire. The Greeks in turn longed to be rescued by the Russians:

Ακόμη τούτην άνοιξη (ραγιάδες, ραγιάδες)
τούτο το καλοκαίρι (Μωρηά και Ρούμελη),
Οσο νάρθει ο Μόσκοβος (ραγιάδες ραγιάδες)
να φέρει το σεφέρι (Μωρηά και Ρούμελη)!

Just one more spring (ye slaves, ye slaves),
just one more summertime (Morea and Rumeli),
Till Moscow comes
bringing the army down.

The Greeks certainly remember the Orlov Revolt of 1770 a lot more clearly than the Russians do.