dotaaaaaa

10 years ago : Day of Defeat
5 Years ago : Age of chivalry /DIPRIP Warmup
Now : Fistful of Frags

Hearthstone currently.

Planetside 2.

Tribes: Ascend, a really great game. Too bad the community and devs make the game implode, I have to let it go since there were like almost non any active players left on servers this side of the world...

As of recent, Toribash.

I saw Hawken mentioned which is good. I love it due to it not being overly complicated like MechWarrior, (though if you're a customization freak, MW does give you way more options.)

Star Conflict is also really well done (I think), and if blasting other spaceships outta the sky is your kinda thing, then I highly suggest it. Those of you drooling and thinking of Star Citizen may want to just stay on their homepage, constantly refreshing until it actually comes out. :P

Path of Exile.

Dota 2. But before that it was MapleStory, like you OP.

TF2? :<

Secret World - You must have some intellect to solve the puzzles. there are no limits in character development, Lovecraftian stories/monsters, awesome community, etc.

Team Fortress 2, wouldn't be as fun though without in-game or irl friends.

APB: Reloaded.

Dungeons & Dragons 3.5e

League of Legends, Hearthstone

I would say... TERA.

TERA: Rising.

TF2

Dota 2
Transformice

Neverwinter

The Lord of the Rings Online.

exteel

Fistful of frags, TF2, Dota 2

RF Online.