i've played a number of them, but right now im getting into cabal online - the graphics are actually really great and the equipment looks fantastic, as do the skills.
its a very skill based combat system, utilizing powerup skills and combos (timing them takes concentration and is really fun).
here are a few things i like about the game:
1) its very easy to get into, you can easily level up with nothing but doing quests for the first 90 levels, and you get wicked awesome equipment and lots of money from doing them.
2) drops in this game are actually drops of your level, if not higher so you don't need to be stuck with equipment 10 levels lower than you until you find something else. this is one of the first mmorpgs i've really played where you find a drop and can equip it immediately, through all levels.
3) the drop rate is great
4) the upgrading system is in such a way that not everybody will end up with the same equipment, and it is going to be very difficult to get exactly what you want. it doesn't seem like all players are the same once they get a certain point.
5) dungeons. these are great fun. great xp, great drops, great boss battles!
things that i do not like with the game
1) the terrain has some pretty bad hitboxes i guess in some spots, where you'll get stuck on something that to you isn't even there. gets a little annoying.
2) with 50+ mobs hitting you and the crazy awesome looks of the skills, this actually stresses my rig out a little bit and i'll dip below 50 frames here and there.
3) like all MMORPGS it takes time, but this game seems like less of a chore to grind grind grind. but again like all mmorpgs if you actually think about it, you're just wasting all of your time.