For me simple and selective or unigue games is good because having lot of games will make the site looks not familiar eve after many uses.
Having instant deposit and withdrawal for crypto currencies will make them as good one.
I have an opposite opinion about this. If a site has a lot of games, it means they will attract all kind of people and people will not have to move to another sites in order to find their favorite games.
Secondly all the good sites have instant deposit and withdrawals and hence this feature is not something unique.
Many sites having instant deposit but not the withdrawal options,they still follow the queue,so you can consider it as an unique thing as well.When it comes to many games will attract more players the maintaining the site also will be harder so the bugs might occur too often but only few games means flawless experience while playing there.