No, there is more to being a global city than population and a specialized hub. There are ~5M people living in Lagos vs. ~800K people living in SFO, and Lagos is an African hub. SFO's area is 232 sq miles compared to Lagos' 386 sq miles. But that doesn't make a lick of difference in where Lagos stands when it comes to infrastructure and cosmopolitan indices.
You should look at the
Global city categorization, which categorizes London and NYC as Alpha ++ cities, Singapore, Dubai, and six others as Alpha+ cities, and LA, Frankfurt, Mumbai, and 10 others as Alpha cities, and Boston, Zurich, D.C., SFO, and 18 others as Alpha- cities.
On the scale, you don't get to Charlotte until Gamma, along with St. Louis and Tampa (for scale).
In fact, in the Global Cities Index of ~84 cities, Boston is ranked #21 (ahead of San Francisco, Frankfurt, Barcelona, Melbourne, Amsterdam, and Dubai), and Charlotte doesn't even make the list.
When you look at the Global Economic Power Index, Boston is ranked #11, followed by Beijing and SFO. Global Power City Index? #30, followed by Chicago and SFO. Wealth report? #14. Charlotte doesn't even feature on these indices.
There simply isn't any comparison. I'm sure it's a great city in and of itself, but it is barely a domestic metropolitan city, leave alone a global one, and the airport even less so. :) It simply lacks sufficient infrastructure and a cosmopolitan presence.