In my view, litecoin is the coin worth holding from the long-term perspective. It is effectively bitcoin on juice or what bitcoin should have been right from the beginning. As it is unlikely that things are going to change in this space soon if ever, litecoin will remain a widespread payment tool for its simplicity, fast and cheap transactions, pervasiveness. It is unlikely either that people will  be using bitcoin for their daily needs but litecoin fits in here quite nicely if you ask me.

Maybe there are other altcoins worth holing long-term but I'm not aware of them. If only dogecoin - for the fun of it.