High impact PhD thesis? Or just incremental improvement? As a PhD candidate, I finally got my first conference paper published in a good reputation conference. My professor said that, even though the paper contained good theory and analysis, the results were only of incremental improvement over the state of the art techniques. He told me that I need to come up with another idea that is big (i.e., has substantial improvement over competing techniques) to be able to graduate. Even though I felt disappointed, I tried to accepted his comment as a challenge to make myself feel better.

Do you think my professor is right? Don't you think that a PhD should be centered around well defining/formulating your problem and proposing/evaluating feasible solution(s), regardless wether incremental or not, as long as originality is preserved. I tend to -respectfully- disagree with my supervisor, and hope that someone else can convince me otherwise. Any thoughts?
AFAIK, to have a PhD you must make a significant original contribution to the field. Therefore, I'm inclined to agree with your advisor. Incidentally, your advisor has considerably more experience at this, trust him.

And yes, @jakebeal is right, likely duplicate of What makes someone deserving of a Ph D?