I pretty much agree with the two previous replies. I mean, there's a selection of songs I don't really mind that much if at all, but can't say I feel any real antipathy towards them either.
But it's one of those things that, in my opinion, makes Iron Maiden such a great band. Even with some weaker studio albums and a handful of more or less annoying traits when it comes to recording approach, productivity and whatnot, I I think they've kept fairly high standard thorough their extensive career.
Quality control didn't really peak during the 90's, yes, and Steve's growing dominance as that particular decade went on hit some bottoms during Virtual XI days, but as it is, I find it relatively good record nonetheless.
Even the weaker albums, say No Prayer, FOTD and Virtual (yes yes you can count The X-Factor if you want, but I love it), have more or less defined musical narrative and cohesion - well maybe FOTD not that much - and it's not like every single riff and idea someone could come up with is thrown in... at least without at least some hint or shade of something actually interesting vaguely existing in it.
While I quite like a handful of late 90's stuff by Metallica, I wouldn't exactly say that Maiden ever created anything as jarring and dragging as ReLoad, for example. There's a lot of good in it, but a fair amount of garbage too. For a band with 16 studio albums, I think even at their weakest Maiden didn't really... eh, exaggerate quite as much as one would probably expect. Yeah the chorus repeats and few other things with Virtual XI got near that, but even though quite uninspired in relation to it's total runtime and total amount of songs, it's not taken that far. And as for more bloated Maiden records, say The X-Factor, TFF and TBOS, I think they have very strong cohesion and fairly good grip on the listener. Of course, it's easy to say that as a huge fan, but you know...
The point was, I think, to merely underline that for a band with some unbelievably stubborn determination at few technical things in recording and some questionable missteps or whatnot, the overall quality-quantity relation on their discography is very, very good.
Of course, with a handful of albums, it comes down to the fine line between ok-good consistency vs nah-mediocre consistency, but yeah, can't really name many songs I really dislike. I used to have some soft spot for Weekend Warrior like... years ago, but it has become somewhat of a contender now though. And there's some annoying moments here and there on other instances, as I've never been too thrilled about Invaders for example, but it's much closer to something just being not really that interesting rather than me actually disliking it.
I guess it's just another fine and very debatable line, though.