People please go back and read the thread. The question wasn’t actually about loving Steve Harris the man or Iron Maiden as a band. The question was asking why he always came so high in best bass players of all time poll.
This is a bit of a word dump (I address my feeling about him as a player before getting down to him cleaning up the lists but here goes


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When I was a younger and much more naïve bassist (who did love Maiden, mind) I was obviously impressed by Steve's right hand technique and the speed of his fretting hand. However, I found him overrated in the sense that his lines didn't blow me away like an Entwistle, and I felt that a lot of the worship I saw of him was unwarranted from a technical perspective. I also found a lot of Maiden's biggest hits not that difficult to play if you slow them down sufficiently, and I foolishly thought that was a sign of inferiority. He does ride the root quite a bit at times, moves with the guitar parts, and quite a few of his fills I thought were obvious on a theoretical level, if pretty cool. Then, I eventually realised that you don't have to play complex countermelodies to be a great bassist, and writing a good bassline is not a simple art.
This is the thing (which other members have doubtlessly brought up): he isn't a virtuoso. He isn't a once-in-a-lifetime player or freakish genius. However, his style is actually Jamersonesque in many ways, he plays for the song and spices things up in all the right places. He drives the songs but he doesn't tread on the toes of the other musicians in the band (except maybe volume wise, but I aint no g**tar player whinin' about a good loud bass). I reckon he's a fantastic role model for beginner and intermediate bassists (I'm not a veteran so I won't tread there) - you can learn a lot of practical stuff from learning his lines. If it makes sense on a theoretical level - fantastic! You're making progress with theory! More importantly, he's a no B.S. player who is not content to just chug the root note, and even when he does, you've got those unmistakable Harrisian triplets going on. The man has one of the most recognisable styles of all time. He can play cool melodic basslines too like the intro from Number of the Beast or Phantom of the Opera or Innocent Exile (the early Maiden albums in particular are loaded with these), and even when they aren't too hard they remind you of the virtue of simplicity.
This sort of thing is a large reason why I feel that he cleans up the lists - his lines are distinctive and he stands out as a stage presence (which helps draw in the non-player crowd's votes, as opposed to say someone like Ian Hill of Judas Priest, who hangs back onstage and was the victim of having to dumb down his style for the commercial market as well as bass-unfriendly album mixes), while from the musicians' side, a lot of players have probably cut their teeth learning Maiden lines and really admire his technique.
He has also written most of Maiden's catalogue on his bass, which explains a good deal of his root note riding etc. When it comes down to it, the guitars are following him, not the other way around, even when he stops and lets them go play on. He's a fantastic songwriter imo and his playing is the driving force of the band. He's a big fan of the late great Andy Fraser from Free too, particularly his work on Fire and Water, which probably explains his strongly theoretical approach despite claiming not to know what a scale is.
When it comes down to it, I
would call Steve a great bassist (even if he often crops up too high on lists) because of his influence, impeccable technique, killer hidden-in-plain-sight chops and immediately recognisable style. He ain't no Jaco, Clarke, Entwistle, Jamerson or Bogert, but sometimes you don't have to be. If I could only be as good a player as Steve Harris (and half as cool), I'd be a very happy man. Hope this helps answer your question (if it hasn't been already lol), sorry for how wordy it is. I've been on a bit of a Maiden kick and these are my thoughts on the matter.