First off, let me explain the title: my first contact with this series was a demo of this game. A simple demo, I don't even know how many years ago... I played it for over 100hours. Hence, the "original" Heroes game for me. Also, it was because of the expansion that comes with this game, that I registered here and bought this, as I already had Heroes 2, but I needed the expansion and couldn't get it. So I also have this game to thank for introducing me to this wonderful site.
This game is completely addicting, and the only flaw it had was the small number of campaigns, which, albeit long and challenging (even on easy), there were only 2. Luckily, this one includes the expansion, which means, among other things, FOUR MORE CAMPAIGNS.
I won't be writing much more about this, I will just say that this game can be played by anyone, it can be as hard as you want and can be played for hour-long marathons or only a few turns each time. It's cheap, do yourself a favor and buy it. And Heroes 3 Complete as well.
As a final note: grab a friend and start a hotseat game. It's better than playing board games, and just as brain-exercising. Takes longer too, if you want.