I have played several MMO's, WoW included (Only for a limited time though) But my favorite of all time has to be Mabinogi by Nexon, Same company as Maple Story and Vindictus (V. actually took place in Mabinogi's back story). It is by far the most interesting MMO I have ever seen.
FREE TO PLAY.
I enjoy Mabi more because its freedom of customization, wide variety of skills and abilities, and unique combat system that is a fusion of real time, and turn based Rock-Paper-Scissors.
While the Anime-ish art style, and overall bright feel to the game might turn off some players, it offers a wide variety of character features, clothes, and armors that can allow you to adjust your look to accurately express the feeling you want to convey. Combine hundreds uppon hundreds of outfit choices, along with a full choice of colors (Not 8 or 10 or 24, but near limitless), You have very little risk of ever seeing any two characters look the same.
Unlike many other MMO's where Stronger Armors are unlocked as you level up, all clothings are available to wear as long as you can afford them (With a few, rare exceptions that are limited by other factors). However, just because one outfit is more expensive, doesn't mean it's better. Clothes are split into three levels: Heavy armor, Light Armor, and Clothing. Clothing offers little in terms of protection, while Heavy armor helps, it won't let you take on anything you couldn't take on before (THe combat is unique, more on that later). With this system, you find armor that you like to wear, and don't have to worry about giving up a pair of gloves you like because something with higher stats showed up. Of course, there are still some items that are rare, powerful, and worth bragging about.
In terms of Skills and Abilities, there are three types: Combat, Magic, and Life. Combat skills and Magic skills are Rather self explanatory. The number of skills are rather low, but each one is very useful. Life skills are abilities to create, or do special actions outside of combat. Life skills include the ability to Play and create music, Refine metal to be black smithed into weapons, armor, or items, tailor clothes, or even create a campfire to help battle wiry friends rest and heal. Skills are advanced by first using them enough times, then once you've met the requirements, you use Points accumulated by leveling up to jump it to the next level. While each of the races have a couple race specific skills, none are guided by skill trees or set archetypes. You don't Choose an Archer class, you just rank up archery related skills, and ignore melee skills. But, if down the line, you choose to change to a Fighter, or even a Craftsman, its not impossible to switch.
Every time you level (Or other major event), you gain AP, or Ability points, usually 2 per level. In order to advance a skill, you need to use your AP. As the skills rank up, they require more AP to advance. To fully Master some skills, you may have used hundreds of AP by the end. Unlike in Wow, where Level 80 is considered top, Mabi levels are done differently. You gain them like you would in Wow, Get expierence, gain level, more expierence for higher level, but after a while (1-3 Weeks)You get the option to Reset your level back to zero, while keeping your skills. Top level Mabi payers have total levels in the thousands, while their on screen level may only be 20-40. This allows you to get the 20AP needed to rank a high level skill in a lot less time. Also, you don't get any weaker for resetting, you can still take on the same level enemies you could before resetting.
And the last, but largest Difference is the combat mechanics. If used correctly, a new player with only the base skills can take on monsters a Dozen times as strong, if used incorrectly, a simple rat can take out a pro. At its core, it revolves around 4 Skills that each have their Strengths and weaknesses. Each skill takes a short amount of time to warm up and become active, and Limit the mobility of the user.
1) Defense: Slows the player to a walk while using. Skyrockets the players resistance to damage. If used with a Shield, can turn a One hit kill to one point loss. IF attacked when using defense, the attacker is momentarily stunned and open for retaliation.
2)Smash: Player can still run around while loading this skill. Skyrockets the players attack. One super strong attack that can do upwards of 200%-400% normal attack power. On the down side, all it takes is any other attack to cancel it. When used against De fence skill, it ignores the raised defenses, breaking straight through. Will send the target flying backwards.
3)Counter: Player stands still while loading and using skill. Drains energy needed to fight. If attacked with a Melee attack while countering, No damage is taken and Original attack plus extra is delivered back to the attacker. Devastating against Smash, Useless against Ranged attack.
4)Windmill: Only AOE attack, stand in one place, and when ready unleash a spinning kick that hits any monster in its range. Very useful when used as a counter after begin knocked back. Downside is it takes 10 Percent of your max health each time you use it.
There are several more combat skills, as well as Magic, Ranged, and Alchemy, who also have their own pros and Cons, but to add them would make this post way too long.
The combat alone sets Mabi apart, as its not just "click-hit-click-hit", If you can get the timing down right you can string together different moves to cause constant havoc and demolish your enemy.
But what is even more appealing is that Its not all about being the best fighter. You can train to be an amazing blacksmith, or create your own music to play. Its not hard to learn, but takes true Skill to master. It is honestly one of the most diverse MMO's I have ever played.
Curious? PM me, and I'll tell you more. I Really like this game.