I think this kind of ranking in not very accurate because you can say a casino is better than others just because it gets more traffic every month.
It might not be totally accurate but I think the data are generated through the traffic too because a good site would always see people going to play with them always and those on bad list would always have low turn out until maybe they adjust their weakness.
The problem is that traffic does not determinate the rank of a casino if we classify them from best to worse. Just take a look at the website on first rank. Freebitco.in is in fact a faucet website that's offering gambling games and also sports book recently. Most of the visits they get on their website come from people who go there just to collect the faucet and not gamble. Same with the website on 2nd rank.
There are also some websites in the top that I've never heard before and they don't even have a thread opened on bitcointalk. That's because they are mostly fiat based casinos that are also accepting bitcoin and that's why they get so much traffic when in fact we can't really call them crypto gambling websites just because they have bitcoin as a payment method.
This is why I said this ranking system is not quite accurate but I understand the OP just created this thread and I support him for the effort he has put in to help this community. He asked for a feedback and recommendations and I said what's my opinion about this.