Well I cant really judge the whole lot as I havent been to very many. But here is my list-
1. Copenhagen CPH - contemporary scandinavian styling, voted best airport by world travellers in 2000.
2. Amsterdam AMS - was a long time ago that I was their but as far as I can remember it was very nice inside.
3. Karup KRP - Small danish domestic airport that has recently undergone modification and looks stunning.
4. Tokyo Narita NRT - A little plain inside Terminal 2, but still a favourite of mine for the Japanese feel of the place
Well there you go