If you mean in term of quality of life, I actually think that in absolute terms it is probably marginal. They might enjoy a more comfortable life, going to places where the normal middle class doesn't go, tasting food which is slightly better. But they don't eat more calories than the average american, if they get sick they will be treated with the same molecules than the average american, the shinny tesla car they will drive will not transport them much better than the cheap Ford of the average american, they will not sleep much better in their big house than the average american, etc.
If you think in term of investment opportunities, clearly there are many investments that are only accessible to wealthy people, because of the amount of risk they involve, or because owning a tiny fractional share of a company is a sort of anomaly. Most investments (building, company, project) have few and require few investors, not the least to ensure proper governance.
But at one point the marginal benefit of the accumulation of wealth becomes zero. I don't think someone who own 1 billions lives much better than someone who owns 50 millions.