The question I need to ask you is if you are referring to the JG Casino or Puarcade extension? If you're talking in regards of JG Casino, it really depends on the demographic of your website. Stay away from the cook-ey slot game as it could make your users lose points.
One thing you should make note of is if you are using a points system like Alphauserpoints, JomSocial's or etc and you allow your members to use the points to bet in the JG Casino. Some of the games that are compatible with JG Casino have high win percentages...your users could gain a lot of points fast. Thanks to the JG community (including me), we advised Vanama to put in some safeguards to prevent members from winning too much.
For example on my website I use AUP as my primary points system. In the JG Casino I use the regular points system included with JG Casino and my members can exchange the AUP points to the JG Casino points and vice versa. I have a HIGH ratio so users can't get too many points through the JG Casino.
The best games in my opinion are the games that have the high winning percentages like Big Kahuna Slot, Cherry Pickin Slot and Mermaids Millions Slot.