I'll add Heroes of Newerth. I could say Defense of the Ancients, but as this is a map in Warcraft lll a game, Heroes of Newerth is suited better here.
Really, what you have to have played before you die is the phenomenon of DotA, an AoS based map that has taken the world by storm.
Really, this is simply the most balanced semi-strategic multiplayer game I have ever played.
__
I prefer HoN over DotA, because it has some visual perks and is also more intuitive as it has it's own engine and is not merely a map in Warcraft lll. I should also add that League of Legends appears to be more unstable, and definitely doesn't look appealing from my perspective. But alas, all three of these, HoN, DotA & LoL, are a type of carefully crafted gameplay mechanics that work incredibly well.