I never had the distinct luxury of imagining Anakin and Vader as separate characters. I was seven years old when I first saw Star Wars in 1982 and was told that in Empire Vader was revealed as Luke's father. At that age, it didn't occur to me to reject the official, canonical tale.

Therefore, I imagined the battle as taking place above a huge lava pit (though not on a volcanic world) with Vader enraged at Obi-Wan for taking his children from him. He wanted his children to follow in his footsteps and surpass him, whereas Obi-Wan wanted to shelter them from the Dark Side. In my seven year old version, the duel would have started in the very beginning of the movie and come to an end around the time that the movie ended. Sextagenarian George Lucas had just a little more restraint in ROTS than I did before ROTJ.