I voted for Beast Over Hammersmith.
Live After Death - production is great, but Bruce isn't in top-shape.
A Real Live/Dead One - Bruce sounds mostly uninspired and every song from this 2 albums has a better live version.
Live At Donington - great setlist, concert & performance, but bad production & picture quality.
Rock In Rio - 2nd best, everything is perfect.
Beast Over Hammersmith - most of TNOTB songs sound better on this album than in studio, Hallowed Be Thy Name particularly.
BBC Archives - I listened this album only once, and I remember that Bruce sounds really, really awful on 1988 performances.
Death On The Road - setlist is OK, but I think that better solution would've been if they mixed up DOD songs + Lord Of The Flies with some of the songs played on The Early Days tour, like Remember Tomorrow or Prowler...
Flight 666 - songs that also appeared on LAD sound better on LAD. I'd prefer to watch the DVD of this than to listen to the CD.
I think that Maiden Japan (remastered release has 17 songs) and Maiden England (also released on CD:
http://metal-archives.com/release.php?id=11174) should be included.