It's definitely Denver International Airport for me, just one of the most unique airports I've ever been to, and I've been to decent number of airports. Denver's tent-like engineering structure is great.
Denver International is the best imo, as previous poster said its a one of a kind, you can play video games/be on the internet as you wait for departure, the structure is very nice...
others of note:
SFO (always hectic and kinda dirty)
SJC (pretty small and clean, not many unique features though)
LAX (slightly above average)
La Guardia NY (trashy)
St. Louis (pretty classy, but not the best)
Detroit is the oldest dirtiest airport besides D.C . Detroit You're just naming airports you've been too, because if you've been to more then 10 then Detroit is the one you tell your friends how ratty it is and leave off the list.
Miami and fort Lauderdales airports are really nice/new.
No man, Detroits airport is really well run and is huge. It's not that dirty and looks very futuristic with the train and the decorations etc.
Anyways, some other ones that are really good are Frankfurt (Germany) and Split(Serbia or something).
I travel ALOT, so I usually ask my self this to pass the time, the PSP eventually dies so I have to do something.
Vegas airport was amazing. I landed at night! You see all the lights, colors, flashes etc. It's pretty impressive just dropping down, then when you go in it's awesome as well.
I've been to Dulles International, Baltimore-Washington (BWI), Reagan National, Ft. Lauterdale, Cleveland, Cincinatti, Toledo, and Detroit. Detroit is easily the nicest, very futuristic and clean, whoever said it was old and ratty is retarded.
BWI is pretty big but I don't recall. Bradley, CT is real lame.
THe worst of them all.. my god.. Dhaka, Bangladesh. That's a travesty. Went there during monsoon season and it looked so dam ghetto. The one in the Abu Dhabi, United Arab Emirates is pretty neatly organized. But the floors and ceilings are f*ckin purple and green. Can you say Barney?
Jeddah, Saudi Arabia and Karachi, Pakistan are okay.