Is there any truth in belief of judgement day?

mslims and christians believe that after some years there will be judgement day. they believe that god will send believers to eternal heaven even if they are bad people like laden, hitler, bush etc and other religions people to eternal hell even if they are good like buddha, mahatma gandhi, dalai lama etc . is it true? I strongly doubt their belief. Because bad people like laden, saddam, hitler, bush etc will be again bad in heaven too. How god will punish those bad people after judgement day in heaven? If any person did mistake in heaven will god send them back to hell? I think concept of judgement day is wrong. what is your opinion?