I think it's about being more of a outstanding shinobi. If you think about it all the hokages are connected so I think anyone who's under the hashi legacy will be hokage
The legacy
1st Hashirama: because the people chose.
2nd Tobirama: being the brother of hashi
3rd Hiruzen: being the student of the second
4th Minato: being a student of jaryiya who's a student of hiruzen
5th Tsunades: being a student of hiruzen
6th Danzo: being a student of tobirama and partner to hiruzen.
It it might go to kashi who's the student of minato.
Then naruto who's student of jaryia who's the student of hiruzen and son of minato.
Naruto is strong enough, he was strong enough once he fought Pain. Maybe he wasn't mentally strong enough or wise enough, but he definitely was physically strong enough.