'Buying a home in Greece' has this to say-
If a foreigner dies without a will in Greece, his estate may be automatically disposed of under Greek law and the law regarding compulsory heirs applied.
A foreigner resident in Greece is usually permitted to dispose of his Greek assets according to the law of his home country, provided his will is valid under the law of that country. if you've lived in Greece for a long time, it may be necessary for you to create a legal domicile in your home country for the purpose of making a will.
A will made by a foreigner regarding Greek assets isn't invalidated because it doesn't bequeath property in accordance with Greek Law. In practice, Greek law isn't usually applied to foreigners and the disposal of property (buildings or land) in Greece is governed by the national law of the deceased's home country unless there's dispute among the beneficiaries, in which case Greek law is applied.
So, even this is a bit 'woolly', 'should' and 'usually' and 'in practice' is all very well, but what happens if it all goes pear-shaped for your loved ones? So, best spend the money and have a belt and braces approach.
For those of you with complicated families, step children, new partners etc. that you are not married to, think very carefully about what will happen if there is a dispute among the beneficiaries - and you thought living was hard enough!