well i will make a small list based on my personal experience:
betfair
bet365
sportbet
nitrogen
stake ...
We all know that Stake and Primedice have the same management.
Primedice is focused on a single game which is dice. If I am not a dice person, naturally I would not list primedice as my top casino sites. THat is also the main reason they created stake.com. Stake caters other casino games.
And for me I wouldn't actually list nitrogen and sportsbet because those two are well know for their sports betting not for their casino games.
I am not so sure about sportsbet. THey have low odds so gamblers tend to go to other sports betting sites.