Well, to me, if a million people are vibing on it, then it has got to have merit. A million people aren't going to be getting something meaningful out of something that has no meaning. That doesn't mean that it's necessarily the best artist of that genre, since like you said there could be better bands they haven't heard.
I don't personally like any dance-oriented music. And I'll admit that I don't exactly have respect for dance-oriented music. But whose to say what primary objective 'good' music needs to have? There is skill involved in creating a kickass dance beat that's gonna get the whole floor grooving.
Honestly, the majority of my favorite bands are hugely mainstream. From Pink Floyd and Neil Young to Eminem and Pantera, and even bands like Burzum and Cryptopsy are among the most popular in their styles. It's not exactly dance music but I think the principle applies across the board. There may or may not be better bands in the underground, but all the bands at the top have a lot of quality. Great bands with enough exposure will become huge, and even if it's just the corporate masters dealing cards, if so many people like it then there must be something good about it. It's not like people who listen to The Backstreet Boys would literally listen to ANYTHING that gets fed to them. Some people would claim that they would, but that's bullshit. Pop fans are music fans just like anyone else, they listen to the stuff they like, the stuff that moves them and suits their desires.
