Which three? All I can think is hack'n'slash RPGs with Diablo. RTS games existed before Warcraft (Dune and C&C), so I wouldn't personally count StarCraft, and as far as I know WoW didn't define anything either (although it really nailed it by doing everything so well). WoW did have a huge impact though, but I wouldn't call it defining anything. Hearthstone and card games perhaps, or were there popular games in that genre before it? I guess that's two.

Warcraft popularized the RTS genre and also made it the great genre it is today.And while Starcraft didnt innovate anything, since Warcraft already did it, it did perfect the formula, being arguably the best RTS game ever made.And while WOW wasnt the first MMo to be created, it was(again) the one that made the genre popular in the first place, and pioneered many things which are now standards on MMO(which you can see by how many MMO tried to be a WOW clone).Plus diablo as you already mentioned.So yeah, you got there the 3 defining games that made 3 different genres as we have today.

Rockstar for me. Played and loved so many of their games. Haven't ever played a blizzard game and don't intend to either.

You might have an argument with Warcraft/Starcraft but I don't see how it can argued that that WoW has not defined MMOs.  I was into MMOs when it came out and I remember it hitting the scene like a tidal wave.  Ask the average person what they think of when you say "MMO" and they'll probably say "WOW".  It has over 100 million accounts created--and that's for a subscription based service.

Oh my bad. I saw Blizzard, Activision, and Konami.

Rockstar made Red Dead Redemption so they win by default.

Konami destroys both

Now? None of the 3
Historically? Konami > Blizzard > Rockstar

Rockstar and not even close