This is another little-known "bitcoin" of 2014. However, this year is only formally a start-up year. The developers held an ICO on the Poloniex exchange, which ended in scandal: some of them left the team, having embezzled the allocated funds.
The main purpose of creating BTCS was to increase decentralization of bitcoin. Basically, the code of the currency replicates BTC, but the hash algorithm SCRYPT is taken from LiteCoin (LTC).
The world's first cryptocurrency, about which much has been written. During its existence (until August 2017) it went from a few cents to several thousand dollars.
This is the most famous "alternative version" of bitcoin. It appeared in August 2017 at the same time as the updated BTC.
This is another recent bitcoin fork that appeared in October 2017. The main purpose of its creation was to simplify mining (availability to ordinary users without specialized equipment) and increase decentralization of the network.
Like BTG, this currency appeared in October 2017, so it is too early to judge its success. Unlike the above "bitcoins," BTCZ is not a fork of BTC, but of another currency - Zcash (ZEC).