I have stayed at all of those hotels except New York New York...
Trop is older and a little lower dollar - but not terrible. Back tower many times better than the front or garden stuff.
Luxor isn't terrible, rooms just feel funny because of the slant of the outside wall. I also found them a little noisy on the lower floors, as the hallways are open to the casino, so you really only have a door between you and 10,000 noisy slot machines.
MGM is pretty nice, nothing special but the rooms are decent and the food choices in the hotel are pretty good. Don't forget the new monorail:
http://www.lasvegastourism.com/las_vegas_monorails.htm
MGM is one end of the line... doesn't really go specifically to many useful places, but you could take it over to the imperial palace and get out to almost anything at that end of the strip.
Excalibur is, well, VERY average.
Don't forget the Monte Carlo as well, basically one block... after that things are a bit further... aladdin.. Paris, etc.
It's a nice change, I think.
Alex