That's definitely not it.
I disagree with you.
It could possibly be it.
Roger was already the greatest pirate of his era. It was "Roger's era" for a reason.
Never said otherwise.
My point was Luffy possibly aims to be greater than Roger.
Becoming the greatest in any era means doing better than what your predecessor did.
Roger's goal was initially believed to be impossible.
Not farfetched to say surpassing what was taught to be impossible to be even more impossible. If Roger's achievement is impossible, then it certainly makes sense to be surprised by Luffy's goal and it also makes sense of Shanks saying Luffy said the same thing Roger said.
Why would WB and Oden laugh at Roger saying he wants to be the greatest pirate, if he was already one (or at least top 2)?
I think you don't understand something.
Finding the One Piece and conquering the Grand line is something that was called impossible for 800 years.
For 800 years, other people had tried to find the One Piece, and they never did. People didn't even believe it was real, they thought it was a joke at some point. That's why Oden and Whitebeard laughed, because the idea of finding this apparently great treasure that hadn't bee found for 800 years seemed absurd.
Whitebeard was only number 2 because Roger did something that no on else had. Roger and WHitebeard were relatively equal in strength, however, in terms of achievement, Roger surpassed every pirate, he found something that wasn't discovered for 800 years.
Furthermore, even 20 years after Roger died, people still do not believe One Piece exists, they think it's a joke.
Bellamy laughed at Luffy for saying he will find the One Piece, he said it was a myth.
When someone says they'll do something impossible, it's deemed as childish and stupid, that's why Kid said when he said he will find OP, people laughed at him, so he killed them.
Remember when Blackbeard said OP really exists? It's because most people don't believe it exists. Like Skypiea Isdland, people called it a myth, One Piece is seen as a myth, a legend that isn't real.
Thus why Whitebeard in his death had to reiterate ONE PIECE Exists. Why say it exists if it's common knowledge? Most of the world don't believe it.
We take it for granted, the claim about OP and being Pirate King, most of the world believe it is a joke and don't believe it exists. We as readers have knowledge the people of OP don't.
Even before Big Mom was defeated, she asked... does it really exist?
So, when Roger said he'll find the greatest treasure (one piece) Whitebeard and Oden laughed because it seemed silly because no one knew it existed. The idea of some fantastic treasure just seemed like a "ROMANTIC IDEA" thus romance dawn.
Even now, people don't know it really exists, only Roger's crew knows that for sure.
It's like someone telling you there is a billion dollars that can be found somewhere, and no one finds it for 100 years. Of course you'd believe it's a lie. This is something that has not been proven for 800 years.
People still don't believe Roger, so the idea of doing something greater than Roger would indeed seem impossible.
