Yeah, I mean it's super tough to ever do something like this, so I'm glad most of the responses seem to be pretty mature.
For one thing IGN has several HUGE Halo fans, with thousands of games played each, but there's still maps we barely remember. Stuff from Halo 2 Vista, or the final Reach/Halo 4 map packs. So from the perspective of familiarity alone, this was challenging.
The other "problem" is that Halo Multiplayer is like pizza - even when it's bad it's pretty good. There's only about ~20 Halo MP maps that I would say are actually, genuinely not good. So that's what's going to rile people up about this list - the switchover from Not Good to Good is around #80 - so there will be maps in the 80s and 70s that other people think are great. And maybe they are. But we just didn't think so.
It's a really really high quality curve, in other words. There's maps like Powerhouse or Isolation that totally do what they set out to do, fill a role effectively, are fun to play, and they still got pushed low-ish in the rankings not because they aren't good, but just because they aren't better.