What each coin refers to themselves as doesn't really mean anything. Bitcoin is the most likely to go mainstream. It has the most mainstream interest and more venture capitalists are open to Bitcoin startups than any other one. What happens to Litecoin and alternatives no one will know.
I was being sardonic. Goldcoin calls itself the gold standard in digital currencies because it has the name "gold" in its title; but it is without merit. Bitcoin is the gold standard.