Project design and scope: "interesting" vs "incremental" science
You have different but overlapping responsibilities to all three; you can't say that one "overrides" the others. 

You have the responsibility to do "good science." By "good," I do not mean "high-impact" or "prize-winning" or anything like that; I mean "ethical": you carry out your experiments or calculations without trying to achieve a desired outcome to support a preconceived model or explanation. 

You owe your advisor and yourself the same level of professional conduct: do the science properly, and let the results be what they are. You also have the responsibility to respect and properly use the resources your advisor provides: money, facilities, and time. 

Finally, you have a responsibility to yourself: do work that you feel satisfies you, and that keeps you motivated. Don't do research in an area just because that's what's "hot" right now; fads come and go, but good research survives that. Second-rate research likely won't survive.