WC3 as a game was never my favorite, I always preferred the faster paced RTS's to the slower, less unit, micro, hero centric WC3 game.
However I will say that WC3 and it's expansion do one thing tremendously well and that's tell a great story and introduce lots of compelling lore.
That in my opinion is one reason WoW has gone downhill, WoW has never been good at introducing new lore that really capitvates people. Pretty much all the lore that people love about the game came from WC3 and that was vanilla and the first two expansions.
Pretty much everything they've done post WC3-lore has failed to capture the imagination and just doesn't really feel compelling IMO.