Sure. Like [MENTION=73844]gameranand[/MENTION] mentioned those games.
Depending on what type of games you want to try, there are quite a few...
Most famous would be the MOBA games :
1. League of Legends
2. Dota 2
3. Smite (for a more 3rd person feel.)
4. Infinite Crisis (Coming soon
)
FPS team shooters:
1. Planetside 2 - Personal fav.
2. Team Fortress 2
3. Ghost Recon Online (Not sure if its out.. will give this a shot for sure)
4. Heros and Generals (FPS RPG hybrid)
5. Tribes Ascend
Strategic RPG/RTS:
1. Path of Exile (Critically acclaimed and best alternate to Diablo, and in some ways even better.) - Just be prepared to grind like hell and play smart. Very easy to get in over your head.
2. Warcraft III (till lvl 20 i think)
3. Drakensang Online (Poor IAP model)
4. Anno Online
5. Tribal Wars (or something like that... not sure about name)
Action RPG :
1. Vindictus (Hack and Slash) - Currently addicted to this. So far, beautiful IAP implementation where you need to pay to have style, but grind to get best equipment and gear. Very high focus on player skill and crafting, hence a pretty high difficulty reverse curve (gets harder as you progress), but very rewarding.
2. Warframe (TPS)
3. Neverwinter (TPA Classic hybrid) - Played for a bit... loads of fun. But paying money gets you too cool stuff that will make u feel bad watching others. lol. Does not need real money to finish the solo game. Much lesser learning curve than Vindictus.
4. Black Desert Online (Not out yet, but arguably the most anticipated of all)
5. Star Wars : The Old republic (Free all the way and very AAA feel to the game, but very little progression in terms of rewards and experience for free players past lvl 20).
6. Age of Conan. (Again not really best exp for free players)
There are tons of others like Star Trek Online, World of Tanks, DC Universe Online, Marvel Heroes 2015, etc... just google best free to play games.