Never played MM1&2, but I heard there are not really good. MM3 (Amiga version) was not bad, but I was too young for HC dungeon and now I just don't have time for it. Never played World of Xeen and I want to change it in a short time! MM6 is really good, but I was very frustrated by those huge megadungeons. Still have bad dreams about Tomb of VARN. For me, best MM is MM7. Ballancen difficulty, good/evil quests, nice portraits... MM8 was incredibly easy (even without dragons in party) and MM9 is... just weird.