Some alticoins to competite with ethereum in 2018 include:
1. Aeternity
2. Boscoin
3. EOS blockchain
4. Waves
I feel for any technology competition is ideal
I don't think any new altcoin can compete the ETH or Bitcoin also , because it is not a joke for any altcoin .
There are numbers of the altcoins and thousands are the algorithm securities for such coins .
But two coins of same technology can't growth same to each other .
So here it any altcoin will give competition will be wave , of dgb only because these two have performance more better then any other coins .
Here another factor of the growth is also , the time that the altcoin spent with its users , here eth himself is fully trusted because people are using it from long time and have big trust , so without trust even any coin can't beat any other coin , regardless of the technology of that coin .