I honestly prefer either the chronological order or the machete order. I really cannot bring myself to watch the Original Trilogy first and then the Prequel Trilogy. To me, one should always end with Return of the Jedi, because the ending of Return of the Jedi is the most satisfying and fulfilling one. If you watch Revenge of the Sith as the final movie but have no desire to rewatch the Original Trilogy immediately afterwards, then you end the Saga on a depressing note. But if you watch Return of the Jedi as the final movie, you have a happy and satisfying ending and can conclude the Saga on a positive note. So again, I prefer either the chronological order or the machete order, as both orders allow you to watch Revenge of the Sith before Return of the Jedi rather than after, and I think it just makes more sense this way.