Is this game (Kingdom Heroes II) made using Unity?
http://www.youtube.com/watch?v=u6qvjtdC0mA&feature=player_embedded
If this game isn't made using Unity, can Unity make MMORPGs like this game?
No, it's not made with Unity. That game appears to have been made using "BigWorld Tech":
However, it is possible to make MMORPGs in unity, although it's certainly no small task. Try looking at the answer which Lipis linked to in his comment.
Unity can produce any game of any sort if you understand it and how to use it. You just have to actively apply yourself towards achieving those desired results. You won't find a one-click game development solution anywhere (Unless you have tons of money and out-source it to contractors). All the solutions require some level of work on your end. There's an awesome community in Unity to help you if you run into issues.
I'll honestly also say Unity has the best licensing I've ever seen for a game dev tool. Buy license, build as many content as you want.
I hate it when someone tells me I have to buy a new license for EVERY GAME I want to make...like bigworldTech does. Even worse, BigWorldTech then goes ahead and makes you give them 10% of gross earnings from your game....talk about being stingy wallet saps! If someone already bought the license to use your software, per single creation, then leave their gross earnings alone!!!