Lisk is a blockchain platform (with its own Lisk (LSK) cryptocurrency) that aims to make it easier for developers to build decentralized applications (DApps) using JavaScript, one of the most widely used programming languages.
ICON (ICX) is a blockchain platform designed to facilitate interoperability between various blockchain networks and enable the creation of decentralized applications (DApps) that can interact with one another.
Polkadot (DOT) is a blockchain platform and cryptocurrency developed by Dr. Gavin Wood, one of the co-founders of Ethereum and former CTO of the Ethereum Foundation.