Cardano EOS NEO. All other altcoins want to pass ETH to become the second most common currency after bitcoin. But I think it will be very difficult to overcome ETH. The ETH platform is currently popular and widely used in ICO projects. And this will make ETh stronger.
EOS, please...I would stay 1000 miles away from it, every day a new bug is discovered an people are loosing thousand and thousand of dollars, it's even worse then when people find bugs in ethereum's smart contracts (none lately btw)