Yes, numerous betting sites and sportsbooks currently accept ETH and other cryptocurrencies for wagering. Some of these also accept fiat money. Due to the difficulty in recognizing the fiat value of ETH, even when playing with the crypto coin, your balance may be shown in dollars or another fiat currency. While laws vary, as long as online gambling is lawful in the jurisdiction where the casino is located, and cryptocurrency is legal in your jurisdiction, everything should be fine.