I like the third, fifth, and second installments. The third is a classic, the fifth offers something new with interesting graphics, well-thought-out gameplay, and an engaging story. And the second one is my favorite part of the Heroes series; I even played it on a 486! It was my favorite game! And for some reason, everyone seems to have forgotten about it; did almost no one play it?
I have a request for those who respond: please provide well-reasoned opinions about each game, rather than just statements like "3 - great!" It's not very interesting to read that.