.org not the best for a casino site but depends on the name.
I have slot-mcahines.org and would hope that the keywords used will over power the use of a .org extension.
.biz makes more sense i.e casino.biz but are there many successful .biz sites out there at the moment.
.info ok for guide to casinos but can't see it being a great revenue maker.
.ws who knows?
In my opinion, it is not so much the tld, but the names itself. Nothing of course will beat a .com but don't overlook the other tld's.
If a name is keyword rich such as slot-machines.org and you can design a killer site that gets ranked high in search engines, i am sure that you will do well.
Whose to say that every gambler online really knows the meaning of the different tld's available to us today.
In closing if a site looks good, gets traffic and makes money, does it really matter what's on the end?