Original MM games are a totally different thing from Heroes of MM.
Ever played Eye of the Beholder saga? Pretty much like that, but without d&d rules and with many added cool features (flying, some randomization, advanced party progression management, etc) and -huge- worlds to explore.
If you don't mind bad graphics, even pre-6 MM were good stuff.
But I'd say 6 and 8 were the best of the saga.