Great list and even better reasoning1. Powerslave : All time favorite of mine. I have a pretty big flag of it hanging on the wall next to my bed. Amazing usage of colours, a creative composition and is very much in your face, meeting the power of the album and the album title.
2. Somewhere in Time : A very nice sci-fi work. I love the modelling of Eddie. The details obviously make this cover, always fun to find new things on there.
3. The Final Frontier : I don't think Eddie of this cover is well liked around Maiden fans, but I love it. It looks fierce. And the colours are just fantastic.
4. The Number of the Beast: I like the idea of the Devil controlling Eddie and Eddie controlling Devil. The modelling is again, top notch.
5. A Matter of Life and Death : Very creative. Great shapes, pretty much the perfect colouring for a war themed album. Very obvious that it's a work of a comics artist.
I love the Live After Death and Brave New World covers as well. Killers Eddie is the best Eddie modelling out there but the rest of the cover isn't that good.