I found it strange that people would start with Part II or Part III of the Godfather trilogy. But then I remember that I was spending the night at a friends house when I was like 13, and he put Part III on and I was like, OK I'll watch it. 10 mins in I was baffled and didn't watch the rest.
Second, I don't understand how people can say the flashbacks are confusing. As long as you've seen the first, you understand that they're showing Vito when he was younger, set against Michael's fall as head of the family. It's standard 7th grade irony or juxstaposition.
IMO, the only thing confusing about the flashbacks are who is who. The first time I watched it, I could never remember if someone is supposed to be Clemenza, Tessio or Genco. That threw me off a bit. But the flashbacks as a whole never confused me. They were my favorite parts of the movie from the first time I saw Part II.
I've said it a million times and I'll probably say it a million more. Although Part III is a bit flawed, I can't help but love it to death. Maybe sometimes more than the other movies even though I know the first two are much better.
It's like when you buy a new pair of shoes and they're all nice and shiny and all, but you can't help but still love that ratty pair of shoes with the soles worn down and the laces about to break.
That pretty much sums up my opinion of Part III.