Never seen this thread before today. It's kind of an odd inquiry because most of us are going to have a very skewed view of this.
Donald Trump might be the most famous person in the U.S., and he's certainly instantly recognizable. He might even be the most famous person in the "western world" (North America and Europe. However, I suspect his level of fame is relatively low for the two most populous continents (Asia and Africa). I'd wager to say that Vladimir Putin is probably more famous worldwide that Trump, but a lot of this stuff is very regionalized.
There are probably some soccer guys who are pretty famous worldwide.
I googled "who is the most famous living person," and the first result was a list of 20 people:
1. Dwayne Johnson (LOL)
2. Joe Biden (not more than Trump for sure)
3. Elon Musk
4. Jeff Bezos
5. LeBoner James
6. Kylie Jenner (really...more than Kim?)
7. Robert Downey Jr. (even more LOL than Dwayne Johnson)
8. Cristiano Ronaldo (apparently one of the aforementioned soccer guys)
9. Will Smith
10. Justin Bieber
And so on...a VERY western-centric (primarily U.S.-centric) list.
I hit "reply" before I finished reading the entire post, but yeah, your last sentence nails it. I would consider myself WELL informed, and I'm not sure I could tell the Jenners apart, beyond they are hot. That's a VERY "U.S."-centric list.
Right now, Trump is undoubtedly the answer. And to Bart's point, "and even the people who hate him still pay attention to what he does", I would argue, like Howard Stern famously back in the day, those that hate him follow him MORE.
Paul McCartney has to be up there, though, even if just for longevity purposes. I would mention the Queen as well.