>Good lyrics and good instrumental, expresses a concept well and sticks to that concept throughout the song
The likes of Rammstein are very listenable but cucked as fuck in the lyrics, and not even wholly great in the instrumental, but even though Olavi Mikkonen of Amon Amarth said he heard Rammstein in a lot of his songs written for Versus The World, they're still miles better simply for having a coherent idea behind them.
>Does something unique, or at least better than similar bands
This one, obviously, is limited by what I've listened to, but it's very relevant to how much I like a song. I can't engage with music if the song isn't doing something interesting and new. Bands like Gloryhammer don't do anything unique, strictly speaking, but what they do, they do so much better than everyone else that they stand out anyway.