I hesitate to step in these choppy waters, but ratings are — by their very nature — an entirely subjective process.
The only way to objectively rate songs — outside a focus group with arbitrary guidelines — is through sales of that song, or the times it has been played.
Yes, that only rates a song's popularity, not its quality, but the premises of "it was good enough for someone to pay for it, or to play it" are two of the fairest we have — songs are created to touch people emotionally and people aren't going to pay for them, or play them, if they aren't touched by them on some level.
"Yeah, but that shit doesn't move them like Maiden moves me."
Which, of course, leads us to the issue of how deeply a piece of art can touch us, which is tied to human complexity. The most popular songs are the ones that resonate with the most people. But since people are different, and bring different elements of experience and biochemistry to the party, the things they are most likely to share tend to the common and superficial. It is the deeply personal that resonates the most with an individual; when an artist is able to strike a chord incredibly deeply with some, it is unlikely that artist will hit the mark with most. It's like quantifying the love of a spouse. One person's obnoxious jerk, is another's "you just don't understand him."
On forums like this we try to quantify what we like about songs and why. And we pay attention to the opinions of others and the reasons that shape their opinions. That allows us to filter musical quality through two lenses: how much we like a song, and how much we respect a song. By all the criteria I objectively try to give to my ratings, From Here To Eternity should be squashed by Seventh Son of A Seventh Son. Reading your thoughts only emphasizes that. Yet schlocky Eternity gets my head bobbing and my air guitar strumming every time, while Seventh Son is something I need to be in a specific time and place to enjoy thoroughly, and has never given me the same high. It's not the "pop" factor, because Paschendale rocks my world every single time and Hooks in You makes me cringe. I appreciate 7th Son, I just enjoy Eternity more.
I get the point Nat is making when she talks about about Hooks. In practice, I even agree with her. I always describe Eternity as a guilty pleasure.
But the fact is, I am imposing my own arbitrary criteria and the criteria of those whose opinions I value when I make the call 7th Son is better than Eternity.
If Eternity touches me more than 7th Son, then isn't it, by my standards — the purest and only really important standards of judging art — for me, a better song?

I'm not sure where all that came from. I'm supposed to be going to the grocery store.
More to the point, underrated, or overrated simply means that song is considerably worse, or better, than what the consensus states.
The simple matter is we are about a month away from having every Maiden song from 144-1 rated in order.
That will be a consensus of this board.
And if Drifter is in the 130s somewhere and it is in Delta51pwned's top 50, than he has every right to call it underrated.
(Unlike Eternity, which is not underrated, just misunderstood

)