You specifically said "the numbers are there to show they're the next two". But Messi and Cristiano weren't recognized as "the next two" because of their numbers. This only developed over time. If Ronaldo just skipped his last United and early Madrid years and immediately changed from the flashy but ineffective winger to the out an out striker not contributing much outside of goals, I doubt he would've been considered Messi's rival in the first place. I'm just hoping we don't get another decade of superficial stat comparisons that are very far away from what actually happens on the pitch.
Personally, I'd take Sancho over both of them and I just hope that players like him or Felix, if he develops like at the beginning of the season, won't be out of the conversation because they don't have goal per game ratios around 1. I already think Sancho was better in the last three months than Haaland and you barely read anything of him in this thread. I simply find it sad that the Messi and Ronaldo debate has changed the assessment of top players so much. Nowadays we wouldn't be having Ronaldinho as the best player in the world in the mid 00s but probably, don't know, Diego Forlan, Ruud van Nistelroy, Roy Makaay, Samuel Eto'o or Thierry Henry (he would at least be acceptable I guess). And that annoys me.
I get where you're coming from. I’ve been a big supporter of Sancho, you can find posts of mine where I'm advocating getting him over Haaland, I think he'd be more transformative as I don't think Haaland will be quite as great at United as he's been with Dortmund (but I wouldn't be mad if he came, I just think without Sancho he's not going to be as effective).
CR7's being a rival with Messi had nothing to do with his time at United as a winger, but they scored similar amounts of goals and one played for Madrid, the other for Barcelona. I don't think he was quite just a striker not contributing much else, he had decent assists numbers as well, but regardless, they were rivals more by the fact they were the technical leaders of two rival teams. They weren't considered rivals before then, just two talented players. As far as 'the next two', stats are a record of history, but I agree they're not the be-all to end-all, they're just a fact of events without context. People have been wondering for some time if anybody could come up and do similar to what they've been doing, and we can see in Haaland and Mbappe two young players who are already putting up numbers neither put up at their age, and in Mbappe's case doing something neither has been able to do and that's being effective and scoring in knock out competition of the world cup (nevermind winning it ). It doesn't mean they're going to be better, or even as good, but they're the next best thing coming up.
You're right about one thing though, CR7/Messi for better or for worse, seem to have made the conversation about goals above anything else, I don't even think it's their fault but it's the media's obsession with goals, and I get it, goals are fun and they're the most important thing in football for many, but it's regrettable that it's turned into a situation where we probably will never see someone like Manuel Neuer win a ballon d'or, or Virgil Van Djik and others, basically no one but forwards will have a shot, 9 times out of 10, at the ultimate individual reward.
And this is a tiny aside, but Henry should have been considered the best player in the world over Ronaldinho for at least one of the two years R10 got that consideration, and yet you have some crazy enough to think Dinho deserves to be considered as an all-time great (mainly because of the aesthetics of his game over any sensible reasons), but CR7 and Messi will always be recognized not just for their stats but the fact they kept the motivation and the drive, as well as the insane luck of staying fit and healthy, to put them over the top of all these other legends.