'The X Factor' is one of, if not my favourite Maiden album. I think Blaze is a much better singer than Dianno, and has just as much going for him as Bruce IMO. He has matured and developed his voice heaps since TXF album. If you check out either of the two B L A Z E albums, you will see how powerfull his voice has become.
I think Blaze's voice suits the whole vibe of TXF better than Bruce's would have, and adds to the dark feel of the album.
On the other hand, 'Virtual XI' is one of my least favourite Maiden albums. I like alot of the material on it, but it just doesn't gel as an album.
My problem with NPFTD is the production. It has some great songs on it, but they just sound bad. The live versions of "Tailgunner", "Holy Smoke" and "The Assassin" that I have on the tour version of 'Fear of the Dark' are amazing, probably the best live Maiden material I have heard. Aaahhh well....