JFK and Newark were both depressing. Haven’t been to Singapore but it’s meant to be wonderful. Best airports are the big ones on the way out (more to see and do) and the teeny ones when you land - especially the ones that mean you can get out the main door less than five minutes after getting off the plane.
Longest you’ve spent in an airport? Spent 8 hours in Hong Kong airport as I had to leave my Airbnb and I couldn’t be arsed walking around in the heat with a big bag so just sat in the airport watching tv all day.
Been to Luton last week and can confirm it’s still awful. They’ve completely redone the bit before security though which makes absolutely no sense as the bit after security is a complete shit show still.