In my opinion, the third installment is the most successful and well-developed version. Despite the release of newer Heroes games, HoMM III remains a classic that cannot be replaced. Perhaps there are some minor flaws (for example, the Fortress town is not available). I'm also interested in hearing your opinions on the pros and cons.
I think this is a very philosophical question that requires a thorough analysis of the entire Heroes series. I hope that in about three weeks, I will be able to answer this difficult question (at least I will be able to give an objective assessment of the third game compared to the fifth. There is nothing to compare the fourth game to, as that project failed. I hope the fans of the fourth series will forgive me).