For example if your tittle says "CLICK HERE AND YOU WILL BECOME MILLIONAIRE" and the one above says "Meh." probably, your site will get a few more clicks, maybe because its better optimized than the one above but that's not a factor.
Optimization is not a factor. Reputation, links pointing at you and rich content it is.
Google's algorithms are proprietary, and they have data from tons of sources beyond links (including clicks) that they could be using to guide search relevance. How do you know that they're not?
EDIT: In fact, I recall a guy using MTurk to test this theory. IIRC, He had two similar pages and was having people execute search queries and click on his site to see whether its position would improve as a result of it. Unfortunately, I don't know whether he shared the results.
It's difficult to dissect because there's a general correlation between the sites that are clicked on and the sites that are linked to. (The exception being aggressive linkbait, which everybody clicks on but then feels deceived and doesn't want to link to.)
If someone knows the answer to this, I'd like to know as well.