Out of the classic eight, I reckon it goes:

8 Bantamweight
7 Flyweight
6 Light Heavyweight
5 Lightweight
4 Heavyweight
3 Featherweight
2 Welterweight
1 Middleweight

The Middleweights just edge the Welterweights out, purely because there are a few more household names, at the heavier weight.

Featherweight is the sleeper division, it is packed with quality, thoughout its entire history.

Heavyweight has to come next, as it has produced a lot of the biggest figures (figuratively and literally) in not just Boxing history, but in sports history.

Lightweight, has has a lot of superb fighters; but perhaps lacked the rivalries of the divisions above them, in my list.

Light Heavyweight, has nearly always been deceptively strong, a few absolute stand out champions, but perhaps the division is slightly at a disadvantage of being overshadowed by the Heavyweights.

Flyweight edges out the Bantams just, because of one or two extraordinary champions, but that is not to belittle the Bantams, who have given us some of the most exciting fighters in the sports history.