What do you think which will be the best alternative of bitcoin in 2018? Ethereum, Litecoin, Ripple, Verge or Zcash?
There is nothing that can compare to bitcoin so there is no way that you are going to find an alternative that is going to serve you the way bitcoin would, why not just invest in bitcoin itself if you are looking for something like it? It's not like bitcoin is not going to end up doing well in the long run any way. The coins all have their usefulness and no two coins are alike