Tough one! Wrathchild might be "objectively" more punchy and powerful song with an immense legacy, but from a purely subjective perspective, I tend to prefer The Pilgrim, simply due to more personal significance & association. Sanctuary is fun, but doesn't really do much for me. I kind of like The Alchemist a lot as what it could be, but as it is, it's bit lackluster. Having really enjoeyd the "crowd party" element of the song whenever I've heard Running Free live probably gives it some extra edge.
The Pilgrim
Wrathchild
Running Free
The Alchemist
Sanctuary
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The Mercenary
Wildest Dreams
Gates of Tomorrow
Speed of Light
Death or Glory