Many of these bands might have been big in the 70s, but I only knew them from their hits in the mid/late 80s or early 90s. So Bad Company from the 70s is very different than from the 80s. Heck, even Bon Jovi from the early 90s is much different than the massive hair metal/rock they had going in the mid 80s.
I'm going to poke at Bon Jovi today.
When you hear songs like "Bad Medicine," it's a very different song than say, Jon Bon Jovi's single "Blaze of Glory." Now, I realize that a solo act can be much different than they band itself, but other songs from around that same time by Bon Jovi had the same flavor. Their more recent hits are also very different.
Music changes over time. Sometimes it's a bit of a shock (for me) when I go back and see how it's evolved.
The late 80s/early 90s were the times where I was really discovering my musical self. I was horrified when Jon Bon Jovi had his own single. What about the band that I loved?!
I ended up loving the song and was glued to the TV to watch the music video on MTV every change I got. (And I still, to this day, have never seen Young Guns or Young Guns II.) I wasn't into cowboys or westerns, but man I loved that song to death.
Around the same time (though I think it was released before this song) I also fell in love with "Wanted Dead or Alive." In fact, I loved it so much I ended up hating it from overkill. For better or for worse, SPN brought it back, and I fell back in love it with. Sadly, all I can hear now at a certain part is Sam and Dean singing BADLY instead of beautiful Bon Jovi.
Won't let me embed: Sam and Dean sing Bon Jovi
I like cowboys much better now, both contemporary and classic, as long as there is a flair of science fiction and fantasy to it. But just looking back at some of these songs makes me smile :)