hello!
why are there so many coins to choose from, do they really each have something unique about them?
The reason that there are too many altcoins is that, every altcoins serves a different purpose than others. Some altcoins can be used to buy products and services, some are use for transactions, some altcoins are for betting and gaming. To answer your question yes they have something unique about them. Also one reason that there are so many altcoins is because of competition, every altcoin wants to surpass other altcoins so developers keep on creating altcoins better than other altcoins in terms of service, security and high prices.
Even though they serve different purposes some just share the same agenda and that is to earn money. I often see these "the first" phrases whenever i see them on fb or on there own site. Although it takes time before they are completely released, not all of these altcoins were released on the market. Some may have been released but it is forgetting because it is not daily updated by their own devs.