I played practically all RPGs ever made but the ones I enjoyed the most and have the insanely amazing combat systems are-
1. Dungeon Siege 3
2. Kingdoms of Amalur
3. Dragon Nest
The funny thing about Dungeon Siege 3 is that when I first played the demo I was disappointed to the extent of rage-uninstalling it, but after I few weeks, for some reason, I tried it again and actually took the time to learn the game, and ever since I compare every game's combat to Dungeon Siege 3, it's just that great.
Unfortunately Dungeon Siege 3 was primarily made for consoles so that included linear environment, lack of skill progression and crafting(the graphics, animations, atmosphere, rag doll physics are however top notch).
But still it is my favorite game just because of the amazing combat system that to this day is still unmatched by anything.