Setting
There is no denying that most MMORPGs have a fantasy setting. Some have a sci-fi setting. Very few have a modern day setting. And of those, The Secret World (TSW) is the by far the best one. Inspired by myths and legends, many I'm quite certain you yourself have hard as a child, TSW has a wonderful take on the modern world.
Quests
All games have kill X of this and gather Y of that. Even TSW. But in TSW these are classified as second grade "side quests". The main quests, all fully voiced, are divided in three categories. Action, where combat is on focus. Sabotage, where stealth is in focus. And then the mind blowing Investigation, where your brain and deductive skills will be set to the test. You will need a web browser.
Combat abilities
While you in most games end up with half your screen covered by hot bars for all of your abilities, TSW makes you choose. You have to pick two weapons. From those weapons you have to pick 7 active abilities. And then you can compliment those with 7 passive abilities. This is called your deck. You skills will be tested long before combat, since you have to put together decks for every situation. Players of TCGs will feel at home with this feature.
But, since there are no classes, and you in the end can master all weapons and all abilities on one character, you can make and save and swap between as many decks as you like.
Developers and players
Not so much about the game itself, but the game does have one of the most mature, friendly and calm communities out there. Maybe that is why the developers communicate directly with us on the game forums?