The dude has spent a countless amount of time analyzing different, superheroes, their powers, weaknesses and the various ways said abilities can be utilized creatively in different contexts and how they could be countered.

This means he's sort of like a toned down Batman in terms of strategic ability & creative improvisation but unlike Batman he actually has a superpower (one that's an incredibly strong general ability but he can't control right now).

So as he improves further as a strategist and gains greater control over his power it's easy to see how he'll eventually become the world's strongest hero.

Now I've been caught up on the manga since Chapter 11 came out, and I've always said that Izuku's biggest strength is his endless pool of creativity (kinda like Soma from Food Wars). Since he's lived without a quirk for 15 years in a world full of quirks, he'd have to search for other ways to solve problems without using powers to help, and having this talent along with a powerful quirk is why he'll eventually be #1.