I was told once by a hotel concierge that a job in the hotel industry outside North America is viewed as quite prestigious. Consequently, service levels and hotel "standards" seem to be better/higher there, as hotel employees take pride in their profession.

From my own personal experience, I have to agree that the Hilton in Copenhagen is much "luxurious" than Hilton Las Vegas (or most Hiltons in the US and Canada). I also find Sheratons, Westins etc to be better in Europe than in North America.