I don't think there is such thing as a "good person." The closest definition of such a thing is a person who has a high amount of habits that are the best actions, dispositions, and the like that most efficiently achieve that person's goals. A lot of the following opinion has grown from my new familiarity with the Graves Model of Spiral Dynamics. Objective ethics seems to be a level 4 concept, but I think society is capable of promoting from being a level 4/5 society. I'm currently fringe-involved with a group that is trying to foster a bunch of people into 7's, and then get these people to work together and "see what happens." Hopefully this experiment will have a lot of positive benefit.
Objective Ethics?
The whole concept of ethics and morality has come into question for me lately, and I purposely avoid a definition along those lines. It is natural for humans to form a concept of ethics purely due to our psychological natures as mass-social creatures in our current state of sociological evolution. It is not hard to see that ethics is plagued by a question of its objectivity, or lack thereof.
For actions, I can think of no action that is everywhere and at all times "good" or "wrong." Some actions are good only in extreme circumstances, but I can still think of times where it is appropriate or at least blurry to perform that action...even murder, rape, and the actions that generally provoke a visceral reaction of disgust can be justified under some circumstance, albeit an extreme or rare event.
Intuitionistic Ethics
With that in mind, it is extremely hard to sum up a person's entire set of reasoning for performing an action as "good" or "bad." Situations are always complex. Our motivations are always complex. We as people far to often make the mistake of thinking we can explain things simply in such terms like right and wrong without needing to know the whole situation.
For example, I once had a boss that was really rude to customers late for their appointments. They had a difficult time finding the building we were in because it was completely unmarked, the customer was from out of town, and they were about to take a really important test that could determine employment or education for them, so they were under stress. Still, my boss refused to acknowledge the complexity of the situation and instead insisted that they were irresponsible and sometimes stupid people that won't possibly pass their test. Of course she was shown to be wrong more often then not, but still had the arrogance and, honestly, incompetence to assume she could derive their personality from a grossly over simplified model.
With this in mind, you can easily see how fallible we are when judging the rightness or wrongness of actions, even when the actions seem far out there (such as murder or rape). Luckily, all humans are gifted with an strong intuition, and we can very very rapidly and holistically size up a situation and determine a correct response even when not all the variables are consciously accounted for.
Are Killers "Bad" Then?
So what do we do about serial killers, rapists, and people that really do bad things? Of course, their selfish motives are far more common then the circumstance where you have to murder one to save 10,000 scenario. It is really simple to fix this problem: see them as cognitive scientists see the mind and doctors see the body. See them as a machine. Or, more accurately, parts of a machine (the machine of society). They're obviously very broken and dysfunctional parts of that machine, and are working counter to the goals of society and so need to be fixed.
Society
Yes, I did say "counter to the goals of society and so need to be fixed" in that last section. I know it sounds strangely fascist, but it's really not because that's not how it is meant (I abhor fascism and find such governments to be extremely limited and incompetent). See this comment in a deeper way. On the surface a protest that does not allow the military to cross a picket line seems to run counter to the goals of society (when in truth only runs counter to the goals of the government, which is not the same as society). However, seen in a deeper sense, it runs parallel to the goals of society, as the ultimate goal is to allow the citizens to pursue a happy life through giving them the freedoms to express their opinions/person, through giving them relative security, and giving them the opportunity and tools to technologically, socially, and personally innovate.
Rough Conclusion
So barring ethics, defining a "good" person is difficult. However, I think it is much more possible then a definition lying in ethical actions. Simply, a pragmatic approach of "fostering techniques and dispositions that accomplish one's goals effectively" suffices for a rough definition, which is the best you'll get with an rough question about something as vague as "goodness."
