Did The Mirage and MGM Grand use to be 5 star resorts when they first opened? Now they are 4?

They were never 5-star resorts. The MGM might have some rooms that are 4-5star. But overall both hotels are in the 3.5star range. Their is nothing super special about either. When you are in the rooms, even the suites, it doesn't feel super luxurious like Wynn, Encore, The Hotel, Palazzo, etc.