Well beyond the basics of safe docks, I guess it comes down to cleanliness and friendliness.
I expect reliable power, clean water, wifi. Showers and a restaurant are good, certainly in hotter climates a pool is attractive.
I don't expect to be ripped off financially. I am happy to pay a good price for a good service but I get pretty pissed off when I am charged a high price for mediocre to poor service and/or facilities.
One of my pet grumbles is badly treated local staff in poorer countries who are exploited by the management-nothing can be guaranteed to destroy the atmosphere of a marina faster!