It's more interesting to play the third game because it has both large and small maps, as well as random ones, while in the fifth game there are only small maps and no randomness, and there are fewer artifacts. I'm not arguing that the graphics are great, but until a more flexible version (in terms of maps, etc.) of the fifth game is released, it will be difficult for it to compete with the third.
Hmm, what does "only small maps and no randomness" mean? Maybe you should take a closer look at the fifth game instead of just criticizing it. There are four map sizes, and there is a random map generator... And there will be more artifacts, including composite ones, after the second expansion (just as not all the variety appeared in the third game right away).
Nothing was better than the third game, and most likely nothing ever will be – it's a masterpiece!
The fourth game is unplayable, and the fifth is already more like Demigods than Heroes; it's a completely different game.
The developers should not have made stupid sequels, but instead should have improved and updated the third game, adding, for example, new factions, artifacts, neutral units, and magic, and that's all that's needed; everything was already perfect.
But why make the same third game again? I've been playing it for eight years and I already paid for it. And I don't want to wait four years to get the same thing plus two castles (no matter what kind). When I launch the fifth game, it's a new game; yes, it's similar to Heroes, and I don't have to study manuals to learn how to play, BUT it's a new game, and I really like it.