Yes, there are 6-star and 7-star hotels -- but only unofficially. The maximum official rating recognized globally is 5-star.
Dubai's Burj Al Arab was the first to be described as a 7-star hotel, and several more have followed since. There are just a handful of hotels in the world that have been loosely classed as 6-star or 7-star, and its easy to see why -- they go all out for luxury, opulence and such unique extravagances that 5-star doesn't suffice. The term was coined as a superlative rather than an actual rating. It's meant to signify the extreme glitz that takes these hotels over the 5-star mark, so they usually skip 6 and sit at 7-stars.
At each one, privacy is paramount and you're treated like royalty. Think helicopter transfers, 24-hour butler service, personal attendants, gold-plate everywhere and a fleet of luxury cars. Maybe even yachts!