Imagine you want to buy some drugs. You know you must be anonymous but you are not skilled IT specialist and you don't want to spend a lot of time searching information about anonymity so you do just quick research on Google like “the most anonymous cryptocurrency”. In every article, Monero is mentioned and is generally considered to be the most anonymous cryptocurrency. I would compare Monero vs. other anonymous cryptocurrencies is like Bitcoin vs. other cryptocurrencies.

Basically, if you want to pay by cryptocurrencies you will probably use Bitcoin. If you want to pay anonymously you will most likely use Monero. Of course, there is Dash, Zcash or less known Spectrecoin or others. But do you want to risk being caught? Probably not, so probably you won't search for new anonymous currencies which aren't generally considered to be fully anonymous. Another great thing about Monero is that it isn't funded and developed by any legal entity, it's more difficult for governments controlling its faith. Zcash is, for example, privately owned and developed by Zerocoin Electric Coin Company (ZECC) – a government can easily focus on it. Moreover, 20% of each minted block goes directly to that company, you can consider it as a tax.