I love all the HOMM games (except 4 and 5 which are not HOMM games) equally, like they're my own children. But HOMM2 is my favourite son. He's the heir to my throne. He's the one I show favour.
With a lovely, relaxing soundtrack and lovely graphics as well as a terrific storyline, this is the pinnacle of turn-based strategy.
Building upon the world and lore laid down in HOMM1 you're thrown into the middle of the battle between the two sons of Lord Ironfist - Roland and Archibold. Roland is on the "good" side, he's honourable and kind and has been bullied by his corrupt brother for years. Lord Ironfist wanted Roland as his heir but through mysterious circumstances he had to flee the castle and Archibold was crowned king. You can choose to help the rightful heir as a Wizard to overthrow his deceitful brother or you can play as Archibold and command the undead to aid you as a Necromancer. The story is further continued later in the Might and Magic games and even with Roland's wife in HOMM3 (however Roland's victory in this game is canon).
HOMM2 also improves a lot of the features from HOMM1. Minor changes such as the "Movement grids" in combat make planning your moves easier. The battlefield is bigger with smaller scale units and there's even reactions from the hero themselves (they may hang their head in shame if it's not looking good or even cheer). The spellbook has been further increased, there's more units (with upgrades!) and... oh I could go on.
The story can only be fully enjoyed if you followed the completion of this game with a playthrough of Might and Magic 6 - 8, which are all canon with Roland's victory and each alludes to eachother.
In closing: The Might and Magic universe is one of the greatest lores around (before it's destruction by Ubisoft) and this is where it truly begins. Pick up this game and wait for Might and Magic 6 to be released. I highly recommend this. Grab it. Go on. You know you want to. I can't put it in enough words.