I love ETH and ETC because you can make your private key and store it in your head. And the network never sees the your key, if you send money offline
You can make your private key by entering it in the MEW, not need to trust to machine or to maker of the wallet in it making
BTC first ETH second, I choose those two because it was tested by time despite the fact that they're both volatile, even if there value increase and decrease happens in a fast phase, people still putting their trust in it and still investing in this currency, I think trust is the biggest factor for their popularity this two was their long time ago you can say that they are one of the pioneers of cryptocurrencies and that is why they are my favorite coin for investments.