Primo, Fredo flat-out says, in that famous boathouse scene, "I'm your older brother, Mike...and I was passed over!" When Michael replies, "That's the way Pop wanted it," Fredo practically screams, "It ain't the way I wanted it!!" That tells me nothing short of the Donship would have satisfied Fredo. It also tells me Fredo had a strong motivation for wanting his brother dead.

Guess we'll have to agree to disagree. In my mind, Fredo was just letting his emotions go in trying to explain his actions after he'd been identified as a traitor.

Lines like "something in it for me" and "I'm not stupid, I'm smart, and I want respect" tell me that Fredo didn't thirst after the ultimate power of Donship; that he would have been satisfied with "something" or anything on his own; and that he simply wanted to be respected by his brothers.
What is certain is that there's no way of proving or disproving either point.

The interesting thing about this message board is that it seems that the more posts you have the more inclined you are to be a Fredo conspiracy theorist.