If someone holds 1 bitcoin in 2023, can he call himself rich ? If not, how many bitcoins holding is equal to being rich in your opinion ?
The term "RICH" is a very broad term.
A person in the street can claim that he's rich. I can also claim that I'm rich. A businessman who is successful can call himself rich. Anybody can say that they're rich. Like I said, the term "RICH" isn't only used in money, but in other concept of life as well.
Now to answer your question if having 1 Bitcoin this 2023 can make him be called as a "RICH" person, yes. I can call myself rich if I have 1 Bitcoin. It all depends on the person who are holding it. If you let Warren Buffet hold 1 Bitcoin, of course that will not make him say that he's rich because even though he don't have 1 Bitcoin, he's rich already. On the other hand, if an Average Joe, or how should I classify myself, maybe a middle income earner like me has 1 Bitcoin, of course I can call myself rich already knowing that our yearly income if being paid at a minimum wage is around $2,650. 1 Bitcoin is worth ~10 years of working time or even more.
Overall, being called as rich doesn't define by how much Bitcoins you have, but to answer your final question, for me I guess having at least 5-10 Bitcoin can make me rich, but TBH, I can call myself rich already even though I only have 1 Bitcoin or even lower.

What you say about the word "RICH" is interesting. What each person thinks of as "rich" is very relative and unique, right? If you say that having one Bitcoin in 2023 makes someone rich, thats a very narrow view. We shouldnt hold Warren Buffet and the average Joe to the same level of wealth. This is about more than just that, though. If how rich something is just depends on your point of view, then the value we give to things like Bitcoin is also subjective.
Lets get to the heart of the matter more. If exactly one Bitcoin is worth ten years of work for a minimum wage worker, then getting that one Bitcoin is like getting ten years of their time back. In a lot of ways, time is more important than money or cryptocurrency. Still, you say that 5–10 Bitcoin can make you feel rich. That tells me you're not just after a number; you want the security, freedom, and power that come with having that much value. Not the Bitcoin itself, but the life it stands for.