Buy this today (September, 2009), start with M&M1, and you'll probably still be playing next June. There is a huge amount of classic fun to be had here just on the first play-throughs. Start with 1, and watch the computer RPG evolve in front of your eyes - the Might and Magic series was one of the pillars early RPG development (along with the Wizardry, Bard's Tale, and Ultima series, all of which I'd love to see here, hint-hint-hint).
These games are long on puzzles, combat, and challenges, perhaps a bit short on story (although there is an interlocking story that links 2 to 5). They also have an enormous amount of replayability - they're full of hidden areas, secret puzzles, easter eggs, and phenomenally difficult (but optional) monsters to kill. Even though the pack comes with hint books, do yourself a favour and play through once without using any hints or clues - you'll have even more fun when you go back the second time and discover some of the things you missed on your first pass.