Here is a tip, kiddos! Just because a band sells a lot of records does not make them good. It just means they found some niche to sell themselves in mass quantities. But is Coldplay a better musical artist than Tom Waits? That isn't even a real argument.
But great bands evolve over time. Radiohead is a classic example. Their first album Pablo Honey sounds like something they made in their garage compared to the consistent gems they would produce over the next couple of decades.
But the three bands that follow found a way to devolve. Many times this was simply because the band wanted to make more money. But a real artist puts their music first, not the almighty dollar.
Three bands that had a meltdown in the 1980s
Aerosmith
There was a point in time when Aerosmith was just starting and wanted to sound something like the Rolling Stones. They were definitely a rock band but with a blues dynamic. In the 1970s, Aerosmith even managed to string together some snappy tunes like "Dream On" and "Walk This Way." Who knew then that the band would turn into a 1980s wasteland?
Maybe the band got horrifically worse Steven Tyler made the decision to give up singing and just started screaming at us. It certainly hurt his voice and he sadly seems to be dealing with that now. But the group that did "Dream On" should have never stooped to offend us with "Angel," and yet the band did in 1987. (Of course, Tyler's drug use didn't help at all.)
Van Halen
The flip happened a bit with Van Halen. They started with David Lee Roth who wasn't a classic singer, but he knew how to entertain. Plus, his voice seemed to mesh well with the rest of the band's fantastic sound on their 1970s albums. "Runnin' with the Devil" on the group's debut album was fun and slapped.
But Eddie Van Halen decided he wanted to bring in a new singer in the mid-80s and Sammy Hagar became the vocalist. A group that was effervescent and rocked went to one that still had great musicianship but an extremely boring singer who allowed the band to do ballads. How fun (not). Simply put, which one do you want: "Jamie's Cryin'" or "Love Walks In"?
Chicago
In the 1970s, Chicago would not have been a band I listened to much, but at least they tried to come up with some creative music. "25 or 6 to 4" from 1970 is a fine song but not exactly the kind most people would play at weddings. The same can be said for 1978's "Take Me Back to Chicago," though admittedly 1976's "If You Leave Me Now" would be.
But the band decided to transpose that last awful tune over to the entire decade of the 1980s when Chicago produced songs so sweet they might rot your teeth (and definitely infected your ears and brain - you might still need to seek medical help for this). 1982's "Hard to Say I'm Sorry" and 1984's "You're the Inspiration"? Gross. If you played this at your wedding, I hope the marriage was better than the drivel Chicago delivered.