I have watched the saga 1-6 many times, and have watched the saga 4-6 hundreds of times, and the problem with the saga 1-6, you have to really be a real diehard SW fans or a lover of Anakins story to want to watch it this way over and over.
The great thing about 4-6, is that those diehards who made it famous aren't necessarily diehard SW fans when it comes to many other movie series. I have so many friends who are just 4-6 fans, and don't like the PT, don't like EU, and aren't interested in the upcoming shows. I have one friend who loves 4-6, but has read countless EU books since 1991 Thrawn Trilogy, and likes the PT, not as much as the OT, but he always says its part of the story.
The thing that makes 4-6 so appealing for replay value, is the story does not need any PT movies, any EU, any TV series to make it complete, it is a lean 3 movie trilogy of one aspect in this huge galaxy that took place. There are more adventures that happen to Han, Leia, and Luke, and there is alot of stuff that happened before the starting of the Original Star Wars, but this story is so great, so fun to watch, just utterly enjoyable, it has the replay value that no movie series will ever possess, even 1-6 now.
The PT is for diehards, and lets put aside all the OT fans that don't like it, it still won't appeal to as huge a base of fans that the OT did in the 80's/90's before the PT. Watching it 1-6, you take away any chance of that fan falling in love with an individual movie that really captures the viewer like it did to us. For everyone of us here, including Jumpman and GoMer, there is one OT movie that captured our imagination, and made us fans for life, and the other two were just gravy.
For me, it is The Orignal SW, and no movie has ever topped that in my life. I love ESB, and I really like ROTJ, but that standalone movie in 1977 made me a SW fan for life, and is the reason I am here right now, cause if it was made with the saga in mind, and was actually more SW-ish, I probably would have never loved it that much. With new fans, and 6 movies now that form the saga, they are either going to fall in love with the saga or not, but they won't fall in love with one movie and enjoy the rest for that reason, because they are watching it in saga terms now.
I really think you will have this diehard niche fanbase of 1-6 fans after it is all said and done, and then you will have the huge majority of OT fans who hate the PT, and think the PT is OK, but that is far different then say 1987 or 1994, when you had this huge OT fanbase, and this other fanbase that just liked The Original SW and not the sequels.
The bottom line is Lucas is targeting his future of SW and his home video releases to GoMer and Jumpman, and it is really writing us off, cause Lucas wants fans to see it 1-6, and that is the difference between Lucas now and 20 years ago, he never used to state how to watch SW, or what is the right way to watch SW, or whose story it was in every interview. He was not paranoid of the movies like he is now, as he constantly goes out of his way to say, "The O-OT does not exist, only the SE, and only 1-6 is the true way to watch it...."
Before the PT, I never thought once about the damn episode #'s, or if it was Lukes story, or the redemption of Vader, cause Lucas wouldn't hammer us over the head in every interview. I just knew the movies as Star Wars, Empire, and Jedi, and the movies spoke for themselves, now it seems like Lucas speaks more for the movies then the movies do.