I think there are a lot of cryptocurrencies that may be as fast or cheap to transact as litecoin, but a lot of them are trying to claim to be more than just a currency (steem for example). I think there is some value in a crypto trying to only be a digital store of value. For example ethereum is great at handling transactions but i don't really think of it as a currency because of how it advertises itself / its trying to do so much more with smart contracts.

I think that compared to the other alt coins that are trying to sell themselves solely as a currency that litecoin's main advantages are
a. its association to bitcoin
b. brand familiarity: people are more familiar with it than something like raiblocks, for now. Its also on coinbase which means there is a good way to get it from fiat directly
c. trust: the network has existed for awhile without any major hacks to my knowledge

I think that if bitcoin began to fail and litecoin was able to distinguish itself well it could actually gain from bitcoins loss value. However if the two are associated as a pair I think this won't be possible.