I live in Romania and I can tell you that we don't really have true luxury hotel accommodation...pretty much the best you can get is a high-quality 4-star experience at one of our Hiltons or the Marriott in Bucharest.

Casa Capsa - www.capsa.ro markets itself as 5-star, but having a friend that worked there, I can tell you it's not the case (at least in terms of service and maintenance).

If the beach is more your thing, the two best properties are Hotel Vega Mamaia ( www.hotelvega.ro ) and Grand Hotel Rex Mamaia ( www.grandhotelrex.ro ). I would say they're decent, but overpriced for what they offer (or better said, for what our beaches have to offer )

If you want to visit the Moldovan region, you could do a lot worse than the Grand Hotel Traian ( www.grandhoteltraian.ro ), designed by Gustav Eiffel and quite nice.