Conflicted. I'll give you my top 4 considerations.

• Pro 1: The reason a lot of these folks become billionaires is because they are able to sell an idea and execute on it. I think that's admirable. I think it's aspirational. I think that is part of the human condition.
• Pro 2: Additionally, they're billionaires because society made them billionaires. Often, they founded a company (or got in on the ground floor), then issued stock to investors. More and more investor's piled on. It's a bit like winning the lottery, only that you (the aspirational billionaire) have some effect in the outcome. Again, I think this is part of the human condition. Civilizations, tribes, companies, whatever you call them, for some bizarre reason that I personally don't quite grasp, prefer to have a leader, or at least will defer to one.
• Con 1: Many people can be millionaires. It's not easy, but with the right vision, gumption, financial know-how, time and a bit of luck, someone pursuing this effort can do so. But, it takes a certain kind of person to be a 100+ millionaire or even billionaire. I think we have enough historical evidence of the type I'm describing - greedy, predatory, manipulative, aggressive, sociopathic. These traits can flourish in business, but I don't think that these are traits that we should encourage in society as a whole. It gives me some gratitude that, for every 1 megalomaniacal billionaire in the world, there were 1000s of lookalikes who flailed.
• Con 2: Rent-seeking behavior and loot dragons. Nothing pisses me off more than a self-entitled dumbass whose entire being is resting on the laurels of a family legacy. I think once the great person's first generation passes, that most of their remaining horde should be returned for the public good. While I do think a certain amount should be endowed to the next generation so that they are equipped to pursue their own marvel, I do think society resources made these people and society should be able to take them back.