When I see people still playing Heroes 3, all I can think of is: Why? Why waste so much time on that game? It's not that good.
It has to be the same kind of person who would incorrectly argue, that Rei is the best girl 25 years after the anime was released.
@Jens_Rasmussen
I was told, that Heroes 5 has a severe limit on the size of map. And although, it could be easily moded now, when it was released, that limit was understandable considering the jump to 3D.
The official maps are well enough crafted, but size limitations might really be a thing, because the use of surface+underground maps is very common, which could be a way to bypass this limitation from the devs.
@Jens_Rasmussen
Also, the Heroes 5 have the common issue of every game, that is re-build from base up. It lacks content from the previous games.
My favorite example is X series.
X3 had 370 ships, while the X4 (we don't talk about the rebirth) has only 214.
I get this trend. It's not easy to invest so much into one game, as it was to invest to Datadisks to already completed one, but it is seriously stripping new games of SO MUCH CONTENT 
@Jens_Rasmussen
Same goes for every aspect of such a sequel.
Here is a map size for example.
This is sad.
@Jens_Rasmussen
Yes, the games are literally called "X" 
https://store.steampowered.com/app/201310/X3_Albion_Prelude/
AND IT'S 2 DOLLARS? 🤯
Edit: sorry, I forgot it's a DLC. 5 dollars total.
@LukeAlmighty Rei is the best girl though.
As for HoMM III; the game doesn’t hold up all that well compared to HoMM V, but if you’re playing on a toaster, wear nostalgia goggles and don’t mind your “cutscenes” as being text-only then it’s quite workable. III also has hexagonal grid for combat instead of V’s square grid, I never understood why the developers made that regression, since hex grid is just pretty much always preferable.