It's amazing how many 727s are still in use. That fact alone indicates that the design was a good one.
I loved the fact that one of them rolled in a thunderstorm with no apparent ill effect. A well made plane. And, of course, the DC9 is a classic as well. Ahh, when it comes to planes, Boeing has made some beautiful ones. I don't know why people think B-52's are ugly...I think they are gorgeous...:) B-17...B-29...etc...etc...etc...