This should come as no surprise since I have posted along these lines in the past, but here is my take on Maiden's discography, album by album (not ranked):
LOVE these releases:
-Number of the Beast
-Piece of Mind
-Somewhere in Time
-Dance of Death
-The Final Frontier
-The Book of Souls
Like these releases:
-Powerslave
-Brave New World
-A Matter of Life and Death
Don't like:
-Killers
-Seventh Son
Don't have/have not listened to:
-Iron Maiden
-No Prayer
-Fear of the Dark
-The X Factor
-Virtual XI
-Senjutsu
Basically, I love most of the '80s "classic" albums, and most of the reunion albums. I don't dislike any of the Bruce albums I have heard, other than Seventh Son, which, other than a couple of songs, does nothing for me whatsoever.
I don't really care for what I've heard of Maiden with singers other than Bruce (although I like those songs that I've heard live where Bruce sings them and they have more energy in a live setting). As far as getting those other albums, I don't really feel an urgent need to be a completeist. Senjutsu doesn't count, as I plan to get that (in fact, it is supposed to arrive tomorrow). As for the rest, I may eventually get around to getting the two '90s Bruce albums that I don't have. Just not much of a priority. Even less of a priority than that would be the Blaze albums. And then Iron Maiden being much, much less of a priority. Honestly, I don't know that I'll ever have enough of a desire to get any of these.
That said, I'm doing a listen-through on those albums that I haven't heard. X Factor is first. I am about 3/4 through it as I type this. My general reactions: I don't hate it, and it is actually mostly better than I was expecting given what I have heard. Here is the major hurdle I have: I have heard Bruce do some of these songs, and they sound much better to me in a live setting. That is partly due to the music just having more energy in general, and Bruce just being a more powerful singer and having an unmatchable live presence. And even though that comparison only holds for the small number of songs I have heard them do live with Bruce, it taints my enjoyment of the entire album, as I can't help but think how much better they would probably sound with Bruce on vocals. There are definitely songs where Blaze does a passable job. But in other places, I just don't feel that he brings enough energy or range to make them sound as good as they could. The production also seems a bit flat and sucks the energy out of the songs a bit. (I feel similarly to a lot of Epica songs, where their studio albums just sound flat and not as heavy or energetic as they should, even though those same songs are amazing in a live setting) But I am definitely hearing some things I like on this album--more than I would have thought. I'm liking quite a few of the tracks Bruce has not sung on. Blood on the World's Hands is a standout to my uninformed ears. But on the ones Bruce has done live, it's just too much of a hurdle for me to enjoy these songs. They just sound like they are missing too much.