Puggo - Jar Jar's Yoda said:

blowing all the reveals

That's really it in a nutshell for why watching the prequels sequels first is a poor choice. George - no matter how much he tries otherwise, says otherwise, or continues to try to force others to do otherwise - cannot change the course of history. A story written & filmed in 2005 cannot come before a story written & filmed in 1977. George's colossal ego can't seem to grasp that very simple fact.

Star Wars came out before Empire, before Return, and twenty years before the three sequels that make up the second trilogy. Watching them in anything other than created order takes away a great deal of their emotion, their depth, and their strength. That's something Lucas quite simply does not understand.

A six-part saga is an interesting idea and it's certainly one that can work - provided it's written and then filmed that way (Harry Potter). The Star Wars series was neither.