People are neither inherently good nor evil because these words are concepts that people have invented. Most of the acts that we consider good benefit the lives of ourselves or others. If it is bad to kill less people die, if it is bad to do drugs less people overdose, if it bad to steal less people are threatened by losing their necessities or the goods they receive from doing the work that benefits others. If people always lost the things they got from working they would be less inclined to work and people would suffer. If it is good to help others more people survive. I believe a lot of the things people describe as good or bad are helpful in an evolutionary/survival sense for the species.
Another problem with this question is that a lot of what we decide is good or bad is determined by culture and is subject to change. This is probably not the case with concepts like murder which we could safely maintain are bad across cultures, but suicide might be considered wrong in one culture and not the next. One culture might find that it is the taking of a life and is therefore wrong or one may find that one has the right to do what one wishes with their own property including their body. This means someone committing suicide might be bad here but not there and so their goodness or badness is not inherent.
If one were to assume that god did not exist would that mean that people are free to act however they want as there is no ultimate moral accountability or that they have a responsibility to act ethically as reasoning beings and should not need someone to be accountable to?