Developer adoption
A project is nothing without people behind it improving it and growing it to new frontiers. The quality and number of developers behind Ethereum are an indicator of how it will look in the future. The more great people work on it, the sooner it will be able to face new challenges that could solve people's problems for increased utility. We can measure developer adoption by the number of dApps published using Ethereum and the number of ERC20 tokens in circulation.
Etherscan, a block explorer, says that there is a total of 164,188 token contracts published on the Ethereum blockchain as of January 24th, 2019. You must consider the fact that many of those are scams. About 1,000 are actually the real ones, considering that, per each good token, there are 10 fake or abandoned tokens. This number indicates to us that Ethereum is the dominant blockchain when it comes to developer adoption, since the others hardly reach a few hundred tokens. People are joining the network and learning more about it for useful purposes because tokens have useful applications behind them.
State of the dApps is the most popular website that congregates most of the applications built on Ethereum. It says that there are 2,432 dApps for this blockchain. This is way more that any other blockchain. However, we must compare it to a real-world scenario where applications are being deployed, since Ethereum is mainly a protocol for building unstoppable applications. Google Play, for instance, lists about 2.6 million active applications, which is more than 1,000 times the size of apps deployed on Ethereum.
We can conclude, based on this data, that Ethereum is, again, in its growing phase, and adoption is just starting, so we must continue building on it until people decide to participate to solve decentralized problems.