There is also slots, you could have probably like a million different slots if you want to, I know it is not really the best game out there but it is still slots. Every big casino makes the bulk of their money from slots because most of the time it doesn't really make you any money, but you usually do not lose all your money very quickly neither, if you have like 100 bucks you can gamble like 0.1 dollars which means 1000 rounds even when you lose all the time, probably close to 2-3k rounds before you run out of money and probably even longer.

So, the best way to keep people on your website and gambling even if it means less income, is slots probably. Also there are a lot of codes available out there as well, and providers too, so it should be very easy to implement.