ETH can accept up to 18 decimal places.
Each ERC20 token has a different divisibility factor which is specified in the token contract. This value is usually 1,000,000,000,000,000,000 (1018) units (which means that most tokens can accept a value up to 18 decimal places), but can vary from token to token. Please check the client constants to see the number of decimal places the token supports.
XRP can accept up to 6 decimal places. BTC, BCH, BTG and LTC can accept up to 8 decimal places.