We all know that Ethereum is the closest Altcoin that can be considered and compared to Bitcoin but it still has a lot of issues and concerns about their Blockchain. What should they improve?
I think Ethereum can't be compared to Bitcoin, it has a totally different use-case. Bitcoin started as payment-coin. Ethereum started as a platform coin where you can create smart contracts and develop for your own use-case (ICOs). So payments are not Ethereum's main function. Comparing I would not say, Bitcoin and Ethereum cannot be better than the opposite.
Ethereum transaction is much faster than Bitcoin.