Well acting=roleplaying. You take control of the characters in a JRPG, but the characters are not "you in the game"... during the story-parts they act according to their own role. The focus of the game lies not only in telling a story. A good RPG tries to make the behaviour, the motivations and the involvement of the character understandable to you. Thats is one main difference to an Action/Adventure in my opinion...
I can't say that your approach to roleplaying is wrong. But there are more roleplaying approaches than this one. You can see even on wikipedia there are given 4 different approaches to roleplaying:
http://en.wikipedia.org/wiki/Role_play
The thrill of a good JRPG is in understanding the characters. Take Final Fantasy X... The game puts much effort in making you realize the inner struggle of Lady Yuna or the consequences of blind belief.
Ok, you could make a WRPG out of FFX. You can create a world endangered by a monster. You can create a situation where you can make a self-sacrifice to safe humanity... YOU are able to decide, YOU can choose. It would work as a WRPG. But it would just be an open world game with a self-created character.
FFX as a JRPG take a different approach. It is not only important if Yuna is willing to self-sacrifice. It gives you a lot of back-story and emotional insight so that you can understand What are the factors that are leading to Yunas decision. It is not that important (or not only) important WHICH decisions she makes... It is very important to understand WHY she is coming to her decision... and this step is missing in a WRPG approach because you are meant to decide which creates a more non-linear story approach.
That was one of my problems with Dragon Age: Origins. I started the story (I think it was female elves) and the first scene dealt with the following situation. My character was together with another Elf on patrol in the forest and we ran into three Humans who entered our forest without permission . After a short dialogue I had to choose
if I should kill all three, one of them or if I let them all life. I was meant to make the decision without knowing any background information. I did not know anything, who they were, who we were, why my partner even treathened to kill them... It was simply impossible for me to make an educated decision. And the bad thing was that I feared that this decision may have an impact on the game in the future that I can't understand right now and that would me make the game restart several hours later... So I feared that I might miss something important or that I would just waste time with a bad decision that I couldn't realize at that moment.
That was my problem with every WRPG that I have played so far. By going the non-linear route with making decisions I felt that the developer sacrificed the depth of the game and a thrilling main story.
So in short... the role-playing aspect of RPGs is that the focus doesn't lie only on the question "What is happening"... there is much effort put into the game to make the gamer understand "Why is this happening". And by focusing on this question I mean going deeper on the topic.







