I think if Jesus came back he's be puzzled at a lot of things and, perhaps, upset.
While there is little debate that Jesus died on a cross we lose perspective in that he was one of thousands to die that way. Cruxifiction actually relates to public and shameful execution for all to see. Some were simply hung from a post by their wrists, some were only tied to a post or cross (the pressure from being suspended with the arms up caused respiratory distress and slow, painful death) and some were, in fact, nailed. As for crosses, there were two types used with one being what is commonly depicted, but some scholars believe the one Jesus died on was probably the more commonly used "T" structure.
In using the cross as a religious symbol, there is some inference that Jesus was one of only a few to die this way. What is unique to Jesus is that he was only left on the cross for hours when it was more common to be left for days, which was often how long it took to die. It is thought that Jesus died more quickly due to an unusally severe flogging prior to cruxifiction. For the most part, the methods and severity of the whole process was usually left to the whims of the executioner.