I practically grew up with this series of games, Heroes II being the first one I've played, and going up to Heroes VI (though couldn't imerse myself in it because my laptop was overheating)Each game was definitely amazing in it's own way, but Heroes V has a special place in my heart.
When it first came out and I started playing it I hated it. I didn't like the graphics, and I had the unluck of starting a mission in underground, which is a bit harder to navigate. So I just said "This game sucks, I'll go back to Heroes IV", until I stayed at a friend of mine which was playing it, and made me fall in love with it.
Top Points for Heroes V:
-Highly interesting story line, with long campaigns for every race
-Two sets of skills (racial and regular)
-A big number of abilities, that can be customized depending on your hero's race (One I liked the most was the "Fallen Knight" where a Knight that took death magic became fallen)
-Awesome combat system and creature abilities, though the expansions increase that even more
-3D cartoonish graphics which has quite some hilarious moments
-A variety of new artifacts
Top Points for Heroes V Expansions (Hammers of Fate and Tribes of the East)
-Two new highly interesting factions, with some awesome combat abilities
-Return of the Heroes IV caravans (i thought without them the game was much harder in Heroes 5)
-Tribes of the East brings another set of evolved creatures to choose from
-Continuation of the story in Heroes V
Overall I found the game experience highly interesting, with a great story line and awesome creatures and incredibly cool spells. I think it's a game that turn-based strategy lovers should definitely give it a try.