To me,
Powerslave = first three tracks and the title track.
Aces High is a killer opener, and the solo duel is what made me fall in love with Iron Maiden (especially Dave's legato section in his solo).
2 Minutes to Midnight is one of those classics nearly everyone knows. One of the first IM songs I listened to. I think it's a good song and one of their heaviest riffs.
Losfer Words is an overall good song, but not as good as
Genghis Khan. Maybe the worst instrumental out of the three they made (
Ides to me is too different, I can't count it among the "instrumentals").
The title track I regard as the best song on the album.
The others:
Flash of the Blade is, to me, one of the worst songs in the "classic era".
Regarding
Duellists I agree with
@Ruflux, it survives thanks to the instrumental section. Also, awful vocal line in the verses. "Classic era"
The Unbeliever.
Back in the Village has their best opening riff, but the song is nothing special to me.
Rime is basically a nearly 14 minutes march which repeats the same gallop half the song. And yes, the lyrics are great, but it's because Harris summarized the original poem tracing it almost word by word.
Even
Killers, which I consider a good album but kinda fluctuating between the "debut" Iron Maiden and the future Iron Maiden, I would rank higher than
Powerslave.
Fortunately, two years later they made their best record (to me).