I think it depends on the person and the performer. Personally, I'd rather do just about anything than see Jimmy Buffet in concert. Aerosmith? I think the years have caught up with them. I'm also passing on Van Halen. Others, yeah, I'll go:
Maiden? They're still releasing new material, and I'd put their latest albums up there with their classics. I love the old stuff, but I'd be happy with a set list that's all post-2000. (Okay, add The Trooper to that list.) Plus Bruce Dickinson is still a heck of a performer.
I saw Judas Priest this fall. It's their last big tour. Halford has slowed down a bit, but he still has a set of pipes. Plus they played for 2 hours, 20 minutes.
Three weeks ago we saw Death Angel, Testament and Anthrax, three big thrash bands from back in the day. All are still releasing new material, and it was a kick-ass show. (In fact, I saw them twice on the same tour.)
GWAR live? Still insane.
Rush? Would you believe I have never seen them. It's on my list.
Dick Dale is not a young man, and we still see him when he passes through Central Florida. He still kills it. Plus he's nice and returns email.
Here's one that surprised the heck out of me. While in college my friend was a big fan of D.R.I.--a punk/metal crossover band. I saw they were still around, and last year they played Orlando. I bought a ticket. I still feel sorry for the opening acts, as these four "geezers" (figure late 40s, easily) blew away the opening acts. Killer, killer show--tons of energy, tight playing, etc. So I did the only rational thing: drove to Atlanta to see them again a few months later--this time with my brother and my friend who got me into them. Again, D.R.I. just killed all three opening acts. Well, they're on tour again....