I really liked Ghost Town. The geometry was a bit awkward to play on, but the lightning/visuals were so enjoyable to me that I didn't mind.
Ghost Town depended so heavily on quality gametype pairings--when it made sense like One Flag, it was a pretty good map. Then you have things like Neutral Bomb Ghost Town, which was just one of those baffling decisions that makes you wonder how these things end up happening. I seem to remember a disturbing amount of Oddball on that map.
Also,
H1: Wizard, Blood Gulch, Battle Creek
H2: Sanctuary, Zanzibar, Headlong
H3: Avalanche, Standoff, The Pit
Reach: Zealot, Powerhouse, Anchor 9
Avoided remakes as much as possible unless there were significant changes, tried to do one large map/two small per game, but there aren't any good large maps in Reach besides Headlong/Ridgeline. I enjoy Hemorrhage despite it being a bad remake, but not enough to push it to the top. I think 2 was full of great remakes that were miles better than the original but wouldn't make the list simply because of their remake status, while 3's remakes largely butchered the originals and should be thrown in the trash.