Most people here will watch the films in the order made but there will be some younger viewers or general newbies who will go chronologically.
Episode 1 is called Episode 1 not Episode -3 so in my book the PT should work both ways, as a film trilogy you watch after the originals to see some of the back story and as the first three episodes which do not spoil the next three.
The problem is that it is impossible for the prequel trilogy to work both ways. It is impossible to have your cake and eat it too. If you watch the prequels as back story after watching the original trilogy, you would want to see a story explaining how Anakin Skywalker becomes Darth Vader. If you watch the prequels as the first three episodes, you would want for the revelation that Anakin Skywalker is Darth Vader to remain secret until the revelation in Episode V. It is logically impossible for the prequels to both explain Anakin’s transformation into Darth Vader and keep it a secret at the same time.