I agree with the author: Heroes II is my favorite of the series, just for the innocent vibe. Also, Heroes IV is underrated. It got bad reviews because it came out buggy, but the bugs were fixed in updates, and of all the HOMM games, it has the best soundtrack.
100% agree, esp. on the soundtrack. I thought I was going crazy when in Witcher 3's Skellige island it started playing the soundtrack from HOMM4. (See Track 14 here: https://youtu.be/F9sG0r_9f4M?t=4400).