Is there a website where I can view the wealth distribution of BTC and different altcoins?
I know such data are only estimates (address != holder, exchange wallets, etc.), but would still like to get a feeling of how different coins are distributed among its holders.
I don't think that you are able to find such information.
It is very difficult to calculate wealth of different hodlers on a blockchain as a user might have acquired more than 1 wallet address.
Even if you find a website which provides such information, it will be accurate probably.