Good faucet need unique design and it should work on all devices. Faucet should have high rewards, at least 15% referral commission. Also it would be good to add games like dice or snake to increase earnings. Or maybe after every claim give lottery tickets. Payments have to be instant to Faucetbox without minimum or low minimal payment direct to wallet (20000-30000 satoshi).
You are right. You said the point: successfully faucets are creative and unique. They have their own system and features.
Default faucets usually have more difficult to get users and make profit, because their method isn't very attractive for many bitcoin enthusiasts.
For me a basic faucet should have:
1. Good or High rewards;
2. Direct payment to FaucetBox or threshold payments to FaucetBox;
For a basic faucet that is enough, but for more elaborated faucets it's nice to see the Dice game, as was said and upgrades or games to earn more. So, if you spend time on the site, you earn more.