I think the real magic is (apart from the solid mechanics) is presentation. I have FUN watching Master of magic. Like, I can watch somebody else play it, which I can't really say about Heroes of Might and Magic, or Age of Wonders.
the diversity of appearance in terrain makes it look interesting enough to look over (where say, age of wonders or Heroes which is usually a fairly solid color background with a bunch of little things that tend to just make the scene look cluttered)
The spells would usually be cast fairly often, and had fun annimations attached them. Not to mention the brief animation for building new buildings (which Age of wonders lacked, but at least a few of the Heroes games had) or reseearching new spells. Spells were cast both in battle and out (I never really felt love for the spells in Heroes games, I guess because I never used them until late-game when I had many levels of spells, and even then it was battle only)
My character I always felt was mine, because it bore my personalized name and appearance (more than Heroes could say), and the choices I picked at the begining I could really feel the direct influence (more than I did in Age of Wonders, which you only really picked the spell books, not like number of tomes or anything like that)
The music. Most of the MoM music was fairly generic and possibly un-memorable (that being said, I CAN remember all of it. Often when it comes to something that relates to founding a city, I "do do da do" the founded a town theme from MoM.) but it REALLY fit! the music really set the mood, and it was very tranquel most of the time, making it very easy to 'sit and play' for hours. I mean, honestly, I think its about the most relaxing midi music that I can think of. I'm kinda shocked I have not heard more remixes of MoM music.
(I really hope that Elemental has trumpets and woodwinds used in a similar way to what MoM tried to carry with the midi music.)