Its either
ETH or
LTC. These two are the best alternative for BTC. These two are huge in every way possible right now especially ETH. LTC is having a fallback right now but its just temporary as far as I know. Get either one for huge profit in the long run.
I will definitely agree with Ethereum, its like the wife of bitcoin.. It recently just hit its new ATH too which is over $1700! currently having its correction so its a good time to bag some of it. Litecoin is still unpredictable one although its a good investment too