Basically I'm not a huge fan of flashbacks, let alone flashforwards, which are so often seen in today's movies!

. In GFII case, however, I don't mind them at all. Somehow I find them to be a natural complement to the story, displaying yesterday's reality in order to explain today's one. On the other hand, there was not such a thing as a prequel at the time GFII was being shot, I think. So it seems to me it was a good technical solution to show us Vito's earlier days. Not to mention that these flashbacks got some of the most poignant scenes of the trilogy.