It needs to be pointed out that two distinct rock subgenres are being discussed here in this thread
(1) The original glam rock, mostly U.K. centered, which started out in the early 1970's as one of the main offshoots of post-pychedelic rock, basically in the opposite direction of another main offshoot that became known as "prog." While in the prog direction, the bands were moving away from simpler, catchier stuff in favor of more complicated, intellectual, serious stuff; in the glam direction the bands moved back toward writing pop hooks and using engaging beats, sometimes incorporating previously abandoned 1950's rock 'n' roll and 1960's power pop influences into their music. Of course there were no strict borderlines between genres... Bands like Wizzard, Sparks, and Queen etc. all used lots of progressive elements early on in their careers, but they were still aiming to be accessible with their material; and prog bands like Genesis, etc. were very visually flamboyant and theatrical onstage. And a lot of the artists lumped together under the "glam" banner were very different sounding from one another. The thing they all had in common though was a sense of theatrical flair, incorporating striking visual elements, costumes, fashions, etc. Some were more subdued, some were more flamboyant.
(2) The later glam rock, mostly U.S. oriented, which peaked in the 1980's, which was an offshoot of mainstream hard rock and commercial metal, and wasn't musically very related to the original type of glam, except that some of the artists were influenced by some of the old school stuff. This was the "hair band" type of glam, which nowadays is often thought of as the main component of what's known by many as "buttrock"... Like the original glam bands, artists under this type liked to be flamboyant with their fashion, hair, onstage theatrics, etc. but in a different way (i.e., it's not at all difficult at first glance to tell the difference between a 1970's glam rocker and a 1980's buttrocker; the differences are pretty obvious).
Typically, you will find people who are big fans of one type or the other, but there aren't too many out there who are crazy about both. Personally, I love much of the original style, and very little of the second type (of the latter style I only enjoy those few who are heavily influenced by the old school).
. 
