I'm guessing you'll find more current or former metalheads here than any other nonclassical genre. I'm not sure why, but Eva Yojimbo proffered a very good theory.
Starthrower, I used to really be into Dream Theater. Saw them 2X and John Petrucci a couple times (once a guitarist, always a guitarist, I guess). I liked Metropolis Pt.2. After a while, I just got sick of it all. It all sounded like endless note-spinning without any purpose. Technically, it's impressive; musically, not so much. That's just my opinion. Again, my opinion; if you disagree I respect your opinion as well. More than anything( nonclassical), I like a good song, and Iron Maiden, Judas Priest, Scorpions, etc. put out good songs in their heyday, which just happened to be heavy. In the 80's I got into Yngwie, bought a Strat and Marshall, and tried to copy him. After a while, I realized it's just endless note-spinning and nearly every solo sounded exactly the same. He's admitted it. He said he worked on a few patterns in the harmonic minor scale, which is unusual for standard rock, some arpeggios, and diminished figures, and he just varies them a little bit, depending on the song. I think Dream Theater is somewhat held back by their lead singer, James Labrie(??). Maybe he has a good voice and range, but the quality of his voice really wears on me after a while.
Having said all that ^ ^, I was fortunate enough to see Maiden on their Powerslave tour, Priest in the early-mid 80's, the Scorpions on their Love at First Sting tour, and many more. I saw Deep Purple 2X on their 1st two comeback albums with the classic Mark II lineup. I was fortunate to get backstage and briefly meet Ritchie Blackmore. Bad Company opened, and I went back to their hotel with them and a bunch of other people. Suffice it to say a certain white powder was flowing as freely and casually as water. LOL!
Merl., I'm jealous you got to see Thin Lizzy with Phil. There's a lot more to that band than The Boys Are Back in Town, but most, nearly all, Americans don't know it. Cheers!
Again, just my opinion. We can disagree without being disagreeable, right?