First of all, it is Bitcoin.  Bitcoin does not have a developed system of smart contracts, but it is the first cryptocurrency that has every chance of becoming the world's reserve currency over time. 

Ethereum also has many direct competitors.  These are cryptocurrencies with a developed system of smart contracts that allow launching solutions of the 2nd and 3rd levels (DeFi, NFT, DAO, algorithmic stablecoins, etc.). 

Among the direct competitors of Ethereum, such ecosystems as Cosmos and Polkadot can be separately noted. 

Solana, Terra, Tezos, Tari, Avalanche are also very promising.  These systems compete with each other.  It is likely that some of them will bring their investors a large profit, and some projects will not achieve significant success in the market. 

But it is also possible that all investments in such crypto projects will make it possible to get a good profit in the medium term.