So after the bad news (sharding won't be implamented until 2020 at best) we can seriously talk about some solid project who can grow in that 2-3 years timeframe and potentially beat ethereum.
I've got 4 good candidates who looks very promising on the tech side (I eliminated marketing and community factors as it'll not last if they don't have the tech to compliment it, EOS,ICX,NEO,TRX for example):
1.Zilliqa- Pbft, the first one to implement network and transaction sharding successfully, extremely fast and secure (in theory at least for now but i personally won't bet against them), new smart contract language called "scilla", similair to solidity but put more emphasis on security. Recently etheromon, the biggest ethereum based game, told they're planning to move to Zilliqa. Vitalik himself dig them.
2.Dfinity- Cloud 3.0, POS, staking is possible, claim infinite scalibility if execute properly
(It's actually possible in theory with the solution they came up with) risking a bit security and decentralization (still better than most), one of the best teams in crypto.
3.Cardano-POS,staking is possible, cannot scale linearly like Zilliqa and Dfinity can, currently kinda centralized but not for a very long time, some very interesting ideas that if implemented could be huge.
4.Hashgraph- DAG, Currently permissioned but has huge plans for public permissionless blockchain in the future, already has big ecosystem and projects who are willing to build on them, could be a serious problem to IOTA.
Hyped projects aren't welcome here and whitepaper projects as well (Harmony, Emotiq,Solana, Aergo and so on)