I have no problem believing:
1.) Jesus was real.
2.) He had some pretty good ideas regarding how we should live.
3.) That he had a demonstrable and major impact on our world/civilization.
What I have a hard time believing is that he "rose from the dead."
What I know from science and medicine is that to be fully dead for 3 days (e.g., no brain activity, a stopped heart, necrotic tissue...) does not come back to life.
I do know of circumstances where a slowed heart rate, undetectablly slow breathing, comatose patient can appear to be dead. And I also know that people in this state may actually regain consciousness.
What I do not know is what evidence would exist that would suggest Jesus was in the "true dead" category vs. the "comatose" version. It is unlikely that such evidence could exist. Even if you had accounts of this comeback, I could not trust thier veracity. It is an extrodinary claim, and one that would require more concrete evidence. Written testimony wouldn't cut it. Would you trust a group of people who said elvis is still alive because they saw him?
So, evidence that would support the resurrection for me would be as follows:
1.) Jesus returning saying that it happened.
2.) A body of Jesus that is 2000 years old and still in viable tact. (Although this would contradict the corporeal assention of Jesus into heaven, it would at least support the unusual circumstances of a resurrection. E.g., it would prove that his body was immune to decay as a result of death)
3.) A demonstration of modern human being dead for three days (in the "dead/dead" way) and returning to life. It would help to also document that this person could ascend corporeally into heaven. Also explain where/what heaven is. It doesn't prove that Jesus resurrected, but it at least proves that it is possible and I would no longer deny it as a possibility.
4.)Or to tackle the problem in another way: Demonstrate that it is impossible for the stone blocking the tomb to have been moved by people other than Jesus.
5.) Or demonstrate that it is impossible for a tomb to be empty for any other reason than a ressurection. (E.g., demosntrate that body thefts/grave robbing never happen)
These are merely examples. But I think that they reflect the kind of evidence that is warrented to support the ressurection story.