The OT is one pretty complete work comprised of three films which- taken as a whole- work well as a story.
The PT is another set of three films which- viewed by themselves- kinda almost make sense and work as their own story.
Some of the names happen to be the same, some of the music happens to be the same and even some of the production staff happens to be the same. There the similarities end. Kinda like comic books- a Spider-Man comic written and illustrated in the 1960s looks and reads very differently from one created last year. Some people like the old ones, some like the new ones and some like both. Yet the creators don't feel a *huge* pressing desire to make continuity water-tight... as long as they sell comics! The two generations never really have to meet.
And as far as Star Wars is concerned to my mind they don't, but that's another story.
Make mine OT!