there are 2 aspects here....the tourism side as well as the nationalities coming to live and work here.
As far as tourism goes, the major european countries continue to bring the majority ie brits, germans, scandanvians and dutch.
However, every nationality is represented here these days with this season seeing an increase from Russia, Slovenia, Slovakia, Serbia, Poland and Hungary. But these nationalities tend to have a shorter season and tighter budgets ie 3 months compared to the rest that provide business for 5/6 months. Is difficult for the local businesses who are used to working for a good 6 months, whereas now they probably just have a really good 3/4 months to make income for the 12 months but unfortunately thats how things are going and you have to accept and make the most of it, hoping that it will develop in the future.
The americans, japanese, spanish tend to just come in on the cruises and spend the day here at Knossos etc and concentrate more on Athens and Santorini.
In terms of nationalities coming to live and work here, the greek government does not make it easy just to turn up here, not UK bashing but is a different ballgame here.... and whilst we have Albanians, Rumanians, Bulgarians, Chinese etc, they know they have to work hard and pay their stamps etc , nothing is for free, as well as face day to day hardships as ' foreigners' as well as certain amount of racism- they seem to be automatically blamed for things when not necessasily so - have witnessed a few unfair experiences of this but probably thats the same everywhere.