There is many alternative coins out there wich should demonstrate significant growth in the mid-term (6-12 months) and long-term (1-3 years) perspective. However, I believe these 10 will demonstrate strongest growth this year:
1) Etherium
2) EOS
3) Stellar
4) IOTA
5) NEO
6) Etherium Classic
7) Binance Coin
Verge
9) Bitcoin Private
10 Aelf