Let me show you what I mean (the capitalized letters represent the word that is accented):
"DO you really want it?" - I question if you want it.
"Do YOU really want it?" - I think that you are acting on the behalf of somebody else.
"Do you REALLY want it?" - I don't think you want it enough to do what it takes.
"Do you really WANT it?" - It isn't something that you should want- like a monkey's paw.
"Do you really want IT?" - I think you really want something else, you just aren't saying what.
Yeah, I know, there are thousands more interpretations that can be inferred - context would help, but that's not my point. My point is that spoken language can be pretty cool.