The third installment rules!!! People played this game, are playing it, and will continue to play it!!! I think the third Heroes is one of the best games.
The fourth one has a lot of new features; at first, I liked it (it was interesting), but then it just got boring. With one hero, you simply clear everything in your path. There's a saying, "one is not a warrior in the field," but in the fourth game, it's the opposite. They abandoned many of the "heroic" elements that were in the previous parts.
The fifth Heroes is a good game, but the third one is still better:D