What's the level of mutual intelligibility/transferrenc between ancient/modern Greek?

[Saldunz]

Armenian. But we're talking a long time ago, like when our words for God would sound more similar. When you had these IE people living in the older Phrygia, before the further stages of migration south and back east across the Hellespont. Armenian itself has subsumed parts of the Anatolian (mainly Luwian, some Hittite; these are IE) and Caucasian (its own family) tongues.

I have read Classical Armenian. It has almost no similarity to Greek beyond some common Indo-European properties, like Latin and Sanskrit.
Actually, morphologically I find Latin and Sanskrit more similar to Greek than Armenian.

I don't think any ancient language would have seemed recognizable to any contemporary speakers of Greek, except for maybe the other really poorly attested Balkan languages (Macedonian, Thracian, Phrygian).