If you were wittiness in a murder and you remained silent then you have a responsibility. If you were supporting crimes, even if you didn't commit them yourself, then again you have responsibility. But you can not hold innocent people responsible just because they are of a certain nation, race or community. So what we should all do is acknowledge the crimes and suffering that occurred in the past. Those who should apologize are only those individuals who were involved in one way or another with the cause of those crimes and suffering.
Beyond that the leaders can also apologize for the wrong doings committed by their side in general. So far Christofias is the only one who did this.