Don't think anyone would compare the Crue to the kings of classic rock like Led Zep, the Who, Stones, Beatles etc.
I will say this though that there has to be something about their music that keeps people coming back even after 20 years. Sure nostalgia has a role in this but even to this day they play crue on the radio. Furthermore, there are plenty of things that I liked 20 years ago that I won't give the time of day today. Getting air play in this day where stars fade in and out pretty quickly is a big feat.
No as musicians they were nothing special. No guitar gods or anything like that but for some reason I still enjoy their songs today. But they write catchy songs and their first four albums have very little filler. That's a pretty good feat in itself too, to have 4 albums that you can play from beginning to end and enjoy almost every song. But more than that the songs are distinct.
Compare that to say Ozzy's no more tears album. While good the songs start to sound a bit alike as far as the rhythm is concerned.
You gotta give credit to a band that can still play places like the ACC 20 years after the fact, rather than say Casino Rama.
Anyways, no they're not in the range of being compared to the legends but they've got enough material to put on a good show where you aren't waiting for one or two hits. Fun band, with a deep library of good songs, and a bit of nostalgia, and a small part in music history (i.e. one of a few bands that gained notoriety and helped start the glam metal explosion of the 80s and took the sex drugs and rock n roll to new heights..... GNR and Poison and even harder bands might not have been signed if it weren't for bands like Crue, Def Leppard, Aerosmith and Van Halen to show that this branch of music was commercially viable) is the appeal for me.
Yeah a midlevel band is a fair assessment but I don't think that takes anything away from what they have done for their own careers and the signing of a ton of poser and forgetable bands of the LA rock scene.
Now take hip hop for example I'm a huge fan of it but I find there aren't many albums that I put on and listen to from beginning to end (even if you discount skits). Run DMC while good sound dated today. LL Cool Jay from the walking with a panther was good but same thing. Public Enemy and Beastie Boys, Erik B and Rakim, BDP/KRS1, Tribe Called Quest, Digable Planets and EPMD get much closer to bands with a number of good albums from beginning to end.
Good groups that you have to track forward on would be NWA, Ice Cube, Ice T, Snoop, 50.
Anyways, just trying to point out that if you look for hip hop groups that have been around for any amount of time and have a large number of albums that you can listen to from beginning to end AND are still as popular today (in terms of crowds they can attract) the list is not that long. So perhaps the Crue deserve a bit more respect.