You don't think "You've Got Another Thing Comin'" isn't a crossover hit? And if you're old enough - like me! - to remember when hard rock acts got played on MTV, you remember Rob standing in the middle of a train track while he was heading out to the highway...
I would give everything you say fair shake and concede that we're arguing which apple tastes better (i.e. impossible) but I will take exception to the very last sentence. Not on your life. No f-----g way. Over The Trooper? Run To The Hills? Flight of Icarus? I don't think I buy that.
Yes, Heading out to the Highway and You've Got Another Thing Comin' (along with Hot Rockin' and Don't Go and, later, Freewheel Burning) got some measure of play on MTV. Does that make any of those songs "classic OUTSIDE their genre" or in any way "transcendent"? Not by any definition of those terms that I would accept as valid.
As far as Peace Sells and the various Maiden tracks you mentioned, I don't think any of those meet the definition either. And, while I personally like the Maiden songs better than anything Megadeth ever did, I do think Peace Sells is on roughly the same level if you're talking about songs that somehow "transcend" beyond the metal genre.