Describing a shitcoin varies from person to person. An alt that made you good money doesn't mean that it's a promising one. So please be honest, and if you ever have to sell your btc, what would you buy with them?
My first vote to Monero, for privacy reasons. Fuk ZEC and its "optional privacy" which is NOT a privacy actually. DASH? Lol, no privacy. Another bitcoin clone methinks.
Second one is Ethereum, there is no serious competitor in smart contract area.
I cannot find third one. Maybe NANO.
None coin is promising to be fair because they don't offer something very valuable which would be considered as promising except one to my mind and that's Monero because of it's privacy, that's why bitcoin is so popular too and monero rocks in this task, it's even better than bitcoin. Also I'm glad that I amn't alone and the only one who thinks so and takes second place for ethereum.
If you are looking for third one, to my mind that can be Grin coin, this coin really revived interest among people, theymos was also very interested with this project from the very begining.