Out of the big bands I'm familiar with:
Black Sabbath - "War Pigs"
Dio - "The Last in Line"
Iron Maiden - "Hallowed Be Thy Name"
Judas Priest - "Breaking the Law"
Metallica - "Seek and Destroy"
Ozzy Osbourne - "Flying High Again"
Rush - "Tom Sawyer"
Slayer - "Dead Skin Mask"
Stuff off the Paranoid album are often overrated (except for "Hand of Doom"), and the non-Ozzy/Dio albums are criminally underrated (and all but expunged from the band in the popular consciousness, thanks to Ozzy having essentially forced Black Sabbath to hitch themselves to his wagon for decades). They could have retired every song off Paranoid and, even if limiting themselves to Ozzy-era songs, had great setlists.
I'm not as familiar with Dio as I am with other big bands, but "The Last in Line" is one of his most radio-played songs, and I just don't see the appeal.
Putting "Hallowed Be Thy Name" has to be some kind of blasphemy, and it's not a bad song by any means, with Bruce's vocals being quite good, the lyrics emotional and impactful, and the musicianship also good, but I think the song is just lacking something. "Run to the Hills" is also pretty overplayed, but I think I'd rather listen to it than "Hallowed..." Of course, I don't think Iron Maiden ever topped the two Di'Anno albums.
I don't know of anyone who actually listens to Judas Priest extensively who really likes "Breaking the Law," but I feel like its their signature song, largely for image reasons.
"Seek and Destroy" is boring. I'm not in the "Metallica was always overrated" camp, but play something else (like "Phantom Lord").
Ozzy's solo career really is overrated - he was always the least important member of early Black Sabbath from a musical perspective. I think I'd rather listen to obscure songs like "S.A.T.O." or even "Believer" before "Flying High Again."
You know what's surprisingly underrated? Synth Rush. "Tom Sawyer" is just overplayed and people who bash post-"Moving Pictures" Rush are missing out. Give me more "Afterimage."
"Dead Skin Mask" is just awful, but I think it was a live staple for some unfathomable reason.