here's my cheeky take:

bitcoin: designed to go up in value over time. solves problem of worldwide zero or negative real interest rates and poor risk return in traditional investments that are manipulated by central banks. also has cool peer-to-peer value transmission and distributed ledger functions.

ethereum: solves problem of hipster masses wanting to be cool yet totally missing the bitcoin boat when it first set sail in 2010. want in on a major cryptocurrency but not necessarily libertarian? ethereum might be the ticket. also solves the problems of bringing smart contracts and kickstarter/over-the-counter bulletin board type stock investments to crypto.

ripple: you are a major banking player and want to make a fortune off this new fangled crypto stuff. you may wish to leave your senior JP Morgan position and scale down to bank consulting and loybbyist work. you create the framework for ripple at a bar in Davos over a few cocktails and install a secret backdoor in the code that makes your future consulting firm indispensable. the XRP lockup period strategy is lifted straight from Bud who was the lead syndicate managing director of the Pets.com and Etoys IPOs in the nineties.

litecoin: solves the problem of how to get all sides to agree on a bitcoin testnet.

ethereum classic: you are a bitcoin maximalist and want to moon some more with this crazy ethereum stuff. after watching a million bitcoin clones go down, you realize that an immutable clone of ethereum with a similar name is a winner. who wouldn't instantly remember that Coke Classic is superior to New Coke?