The one-and-only game my girlfriend got hooked up on.
Visuals: Semi-over-the-top camera and beautiful but low-res. graphics are the first thing that comes in mind. You can't rotate camera, hell, you can't even zoom but somehow it works perfectly the way it is. In fact, all the camera options in HOMM5 made gameplay a bit tedious for me, since I spent more time on trying to get the right angle than on exploration and battles. 2D graphics are vibrant and rich, although from this point low in resolution. However, there is a fine little mod called HOMM3 HD (I think?) that can virtually multiply resolution, squeezing the bast out of a decade old graphics.
Sound: Oh, man, some consider it the best part of the game. It is widely accepted that HOMM2 and 3 both have the awesome soundtrack. There are, of course, ambient sounds of water, wind and forest, birds tweeting etc. which fit perfectly with graphics and overall atmosphere. Also,the music is in mp3 format in a specific folder, so you can actually customize the sound design yourself.
The gameplay is, as always, what makes this game so good. As you already know it is a turn-based strategy/RPG game. But, in fact, it is much more than that. Heroes 3 actually summarize the best elements of traditional board games, such as chess and RPG formulae and lift them on a whole new level. The game has intelligent and delicate learning curve, so that learning the game rules is as interesting as a gameplay itself. The main rules are logical and relatively easy to comprehend, even for people who don't have much experience with RPG. On the other hand, if you want to play on a higher difficulty level you really got to master the tactics aspect of the game. One thing I can guarantee - hundreds of hours of intense gameplay experience. The game is highly addictive and once you get going you are going to abuse it for years. That's right!