Which are the best competitors to Ethereum, and why do you think so?
(I know on top of my head that Cardano and IOTA try to challenge Ethereum,
although they still haven't proved much from my understanding?)
CARDANO and NEO is the best competitor as I know. Other coins and all will not works that like ethereum. People widely choosing the NEO as their platform to create new coin nowadays. Personally I do not like this smart contract implemention and creating new coin all the time. Because I see many attempt has been done in the forum also. Once people invested on token sale then they leave without any information to the investors, some cheap dev team members helping them for money. In price wise Dash and Dodge are competitor for ethereum.
What unique value does NEO bring?
I know that you can use several programming languages, but besides of this, what do NEO bring to the table?
Cardano looks like a threat, but they still haven't delivered anything, but that's the one I'll keep an eye on.