Electryon
Savant
The Might and Magic series, volumes 1-9 (yes, I'll even include the flawed, incomplete last entry in there) are collectively the best series for pure, straight-up fantasy adventuring that have been made. You can argue whether World of Xeen might be better, but Might and Magic VI has everything. One of the most massive worlds in any RPG, a true step-up in technology at the time, endless dungeons against endless enemies, and a totally open, non-linear world, yet one that will still punish you for going where you shouldn't be yet. You can't get more bang for your buck than snatching up this whole series on GOG for what will amount to about 30 dollars, in exchange for which you'll have about 1000 hrs of content at your disposal.
I dunno...I love the M&M series, but I think I'll rate the Gold Box and Wizardry series even higher. MM 3-5 were too much of a disappointment to me with its very simplified combat compared to MM2, and then there's MM9...
I agree those 3 are the main contenders, unfortunately Ultima simply doesn't make the list because the first 3 aren't actually that interesting, and 8 and 9 are FAR worse than Might and Magic's 8 and 9. I do think Might and Magic has the most charm of the 3, is the most addicting gameplay. Gold Box is the ultimate realization of Pen and Paper D&D (even more so than the Infinity Engine) and Wizardry is the most hardcore and challenging.
Might and Magic IX is unfinished more than bad, it still plays just like it's 3 predecessors, it has a great Might and Magic soundtrack, and the dungeons are actually pretty great, as are the class quests. The problem is that (much like the later Ultima games) it was forced out 3-6 months before it was done. The cities are clearly not finished, and some of the quests just aren't fleshed out. I don't think it's the fault of the designers so much as the developer, as has been the case with Troika and Obsidian in later years. They weren't allowed to finish their games.