Best Strategy: Starcraft 2. Starcraft 2 dominated the RTS scene ever since the release of Brood War. It played one of the biggest roles in putting E-sports on the map. It is one of the most popular games ever made. In terms of gameplay, I think it is second to none. Obviously it depends on people liking the real time aspect of it. But it came with a full campaign in Wings of Liberty and Heart of the Swarm, it has a HUGE arcade section where blizzard as well as users make games for others to play. At a competitive gaming level, it is a top 5 game. It just has everything.
Best MMO: This has to be World of Warcraft hands down. I don't think any of the others really have a case. WoW is what every MMO released is compared to. There is a reason that WoW has been here for the better part of a decade while other MMO's die faster than they were created.
Best FPS: I am going to say Battlefield 3. It didn't have that competitive aspect like CoD or TF on a large scale, but gameplay wise it is in a league of its own.
Best RPG: Skyrim. It was just the best. Just an absolutely insane amount of quest lines, items to find, things to do. The graphics were phenomenal when it hit.
That's all I have for now.
Sig Credit: Toxic