After bitcoin, the most popular coin is Ethereum using smart contract feature.
Ethereum initial price value on 07 Aug 2015 was $ 2.83. After one year on 14 March 2016, the price reached $13.82. The price value soar to $17.69 in 17 June 2016, Latest price is approx. USD 350
Yes, Ethereum has grown fast in a short amount of time. But, technically and architecturally it's a platform with some serious challenges!
I don't believe that Ethereum will be able to remain in second place for a long time. I think it will be beaten by another platform sooner than we think! I've written a post about this: https://steemit.com/cryptocurrency/@valderrama/stratis-will-beat-ethereum-in-2018
A first big jump for Stratis will be in Q3 when they will release their Breeze wallet, and Q3 is very very soon. ;)