The better songs have all been eliminated already because of the way the game was structured. This isn't really song vs. song across the catalog, it's song vs. song on a per-album basis, then per groups of albums. Ultra-classic albums only got to send one song forward, often against the winner of another ultra-classic album, so lots of amazing songs got eliminated early.
As far as why "Hell On Earth" is so great, a big part of it is the killer vocal melodies, which are really infectious. It also has a unique song structure, and some really epic and memorable moments ("love in anger, life in danger"), and it has this big, bittersweet feel that's perfect as an album closer.
"Rime" is also great, but it spends a lot of its runtime in a very specific groove. The interlude in the middle is cool, as is the massive buildup back into the heavier part, but I've always felt like it's just a little bit bloated and repetitive. It's nitpicking for sure, as these are both 10/10 songs in my book; but you have to make a decision somehow.