Defiance
A sci-fi MMO third person shooter with decent cutscenes and an intriguing storyline. This is one good game to try out regardless of whether your a fan of its TV series or not...
RIFT
Set in the unique fantasy world of Telara, players of RIFT Online will be expected to fend off constant invasions by myriads of monsters, from other planar dimensions, via closing mysterious portals called Rifts.
Onigiri Online
Although Onigiri Online's mostly about running around following the main storyline and repetitive clearing of dungeons, but the way they've chosen to present things gives (it) a rather entertaining sense of progression, that somewhat makes the game more enjoyable and less of a grind.
APB Reloaded
APB Reloaded is sort of a "free and easy" third person shooter kind of game. Its gameplay (semi-) parallels those "open-ended" games, such as "Grand Theft Auto", where you get to run around a cityscape filled with NPCs walking and driving all over the place.
ArcheAge
A Free-to-Play fantasy sandbox MMORPG where there's no predefined paths of progression and your free to choose your own way of playing the game. However, being a sandbox, the game can be pretty heavy on the grinding though. So consider yourself warned...
Star Trek Online
Whilst not a bad game to play, I kind of find that after the initial freshness is gone, what's leftover is just a repetitive grinding to upgrade your starship, your equipment, your bridge officers and duty officers... Nonetheless, following the storyline is still pretty fun in my opinion...so do give my articles a read and decide for yourself.