Greece is two trips in one. Athens is a real city — a few days of ancient sites, rooftop bars, and taverna dinners — but the reason most people fly here is the islands. The Cyclades (Santorini, Mykonos, Paros, Naxos) are the whitewashed, blue-domed postcard Greece; the Ionian islands (Corfu, Kefalonia, Zakynthos) are greener and calmer; Crete is a country of its own.
The mistake is trying to island-hop too fast. Ferries take longer than the map suggests, and each island deserves two or three nights. A better approach is Athens for two nights, then two islands, each with three or four nights. The ferry and flight connections between them are the part worth planning carefully.
Greek food is simple and excellent: grilled fish, lamb, feta, olive oil, and vegetables. The taverna is the institution — order mezze (small plates), share everything, and let the kitchen decide. Wine is local and cheap; ouzo and tsipouro are the spirits.
Greece suits couples, honeymooners, families, and groups. The water is warm from June, the islands are lively in July and August, and the shoulder months of May, September, and October are the sweet spot for weather and value.