'Filoxenia' ("friend to foreigners"), is an important point of pride for Greeks, and is something rooted in ancient times and in mythology. In the latter, Zeus was said to have disguised himself as a poor man, dressing himself in rags, so that he could visit the homes of Greeks and see how they treated strangers, revealing himself at a certain point as the god he really was, the point of the story being that it's a good idea to treat strangers/foreigners well, because they could turn out to be gods.
The Greek word 'xenos/ xeni' (masculine/ feminine) means 'foreigner' or 'stranger'; making filoxenia/hospitality 'love or friendliness for the foreigner/stranger', who is, in turn, the guest (filoxenoumenos).
In villages, it is not uncommon for villagers to show up at the door of a resident foreigner (or even a temporary visitor renting a room) with a sack full of fresh tomatoes, or even a bottle of local olive oil.
On the other hand, many Greek villagers keep to themselves, with an invisible, but palpable, barrier between their extended families and outsiders. Again, one cannot generalize, and people act differently, too, from place to place.
Many civil servants in Greece, at the telephone company, the national bank, etc. are noticeably cold and indifferent (and often downright rude) to customers, as are a good many salespeople, especially female ones, who will often go on talking with friends or on their mobile phones, with barely a glance in the direction of the customer waiting for help. Once again, there are occaisional exceptions.
In touristic places that see hordes of visitors in the warmer months, Greeks who work in tourist offices, shops, car rentals, hotels, rooms complexes, restaurants, and bars (all the places that serve these visitors) some Greeks have been negatively influenced by rude, demanding, heavy drinking, half-nude, thieving, or otherwise obnoxious types of foreign visitors, or merely by the sheer numbers dealt with every day for up to 12 (or even more) hours, seven days a week for a period of some four or more months.
Many Greeks shield themselves from these types with cold indifference, or even with rudeness of their own, though many are quite professionally (or even warmly) polite. So, on the other hand, enterpreneurial Greeks, working for themselves (of which there are far too few), can be wonderfully helpfull if in the mood.
Certainly many of them have come to regard non-Greeks collectively, an impression that more sensitive visitors to Greece can help to counteract. It is therefore extremely important to visitors to touristic places to keep in mind that the Greek people who serve them during their visits to Greece ( in all the kinds of places mentioned above) endure a brutal work schedule, many of them at very low pay, in order to survive and to feed their families.
Many of them are continually exhausted during the long months of the tourist season, and need to be treated with extreme patience, respect, and sensitivity.
For example, if your boat is late, don't sound off about it to the employee at the ticket office, and when you enter a taverna, if you see that the the dishes are displayed behind the glass 'vee-tree-na' and the place is busy woth customers, save yourself time and go look at the dishes on offer and right then and there order the ones that appeal to your eye rather than sitting at the table and having the wait person try to explain what all the dishes are on the entire menu. Spring is better than fall to visit.