tubegroover, you're right of course. And it isn't a competition. If it was, and sales was the issue, then it would be Michael Jackson....The Eagles are second and fifth place goes to.....Meat Loaf! If it was purely influence it would probably be Elvis. If it was pure Americana or pure talent it would probably be the Band.
For me, the value of threads like this, where people make a case for a certain band or musician is that it gives me ideas of music to try out. Either stuff I've forgotten about, stuff I've never heard or stuff I was sure I didn't like but about which someone had made a good case.
I'm not much of an Eagles fan but when it comes to sales, popularity, prolificness, talent and durability I think they rank pretty high.