I think it has something to do with the recent fansubs of GaoRanger. The melody is the Rouki theme, which is decent but you hear it a lot and get used to it after 10 or so episodes of Rouki owning everyone.
But then GaoSilver appears, the melody is used in his theme song, and BAM! It becomes awesome because it's an old thing we've already associated with a badass character but with a new twist.
Similar things happen with the AbareKiller and GoRaiger themes, but OP didn't consider them sixth senshi (which they technically aren't I guess).
It's just generally awesome when antiheroes finally join the team, and the songs are awesome by association.
I really loved DekaMaster's. wait, Go-onWings' theme is not considered? I loved that one too, although I don't like them.
basically, I love all the themes listed above except Shurikenger, never heard it before.
But then GaoSilver appears, the melody is used in his theme song, and BAM! It becomes awesome because it's an old thing we've already associated with a badass character but with a new twist.
I really loved DekaMaster's. wait, Go-onWings' theme is not considered? I loved that one too, although I don't like them.
basically, I love all the themes listed above except Shurikenger, never heard it before.