We may start talking about rivalry if Mbappe joins a Premier League team that directly challenges City's Haaland, or if both of them move to the godfathers of football rivalry, Madrid and Barca.
Exactly. I have been struggling to explain to some people that I don't mean Haaland or Mbappe won't be individually as big as Messi or Cristiano but rather they won't have a rivalry that would match the latter. Players' rivalries are formed when there are entities bigger than the players fighting. There's a reason we never looked at Suarez, Lewandowski, and Ibrahimovic as rivals.
Those three strikers were never in a consistent, direct competition at the same time. They had no reason to face each other at least twice in a season. You are definitely right.
Even Neymar was talked about regularly at Barcelona. Immediately he moved to PSG in a league where no one was actually competing with him, the dude became a somewhat forgotten man.
Yeah, I remember a period where the Cristiano/Messi fight elevated to be MSN vs BBC.
I never thought of it until you said it, but there was a three years period where I only saw Neymar once, and he was only in the stance during the PSG vs United match.