Think about it they will watch I-III, and then get to Episode IV and have this culture shock at things in the movie:
-They will wonder where is The Emperor and Yoda?
-They will wonder why are these effects so inferior
-They will wonder why the duel between ObiWan & Vader is so slow and lame
-They will be looking for the internal struggle of Vader as this tortured man, and it wasn't even invented til ESB.
-They will wonder why Uncle Owen hates Kenobi & Anakin, when nothing is stated in AOTC or ROTS.
-They will wonder where the Imperial March music is?
-They will probably think it is slow, and not a computer game action fast like the previous movies.
-They probably won't fall in love with Luke, Leia, and Han like we did, cause they will focus on Vader since the story is about him.
It is a shame because I have noticed on other web pages, that newcomers watching it 1-6 put the original SW as their least favorite, cause they are so ingrained to watch the saga now 1-6, and to be the story about Anakin, the original from 1977 wasn't written like this, and they are watching the movie in a totally different context then we did, as we watched it as just the first SW movie. I really feel bad, because no one should think the original SW is an average movie, growing up everyone I knew loved it, and we debated ESB & ROTJ.
The original SW not being loved by the younger or newer SW fans is a direct result of the PT, cause it went from being the first SW movie seen by us, to being thrown into #4 spot, and now it sticks out like a sore thumb. I put the blame on Lucas, cause he says the saga must be watched 1-6 now, and in the process has scewed up the one great SW movie he directed. Thank god I saw it when I did, cause it is still my favorite movie of all-time, now it just another episode in the SW saga, that is sad.