Could a 2/3 majority vote be used as a consensus I understand that Bitcoin currently is using the chain with most proof-of-work as consensus. However could this method be improved, like only allow one block being generated at any given time, and each node verifies this block with its own past data. If there are more than 2/3 nodes prove the block to be valid then the block is added to the chain. If someone wants to create a fake block, then he must control at least 2/3 of the total nodes. What kind of attack is this consensus vulnerable to?
Your proposal is not sufficiently specified:  


How is the authoring node selected?
How does a node prove his authority to author a block?
How do other nodes show support for the published block?
How can the support for a published block be verified by other nodes?


It is not clear how your proposal achieves consensus at all. Additionally, there doesn't seem to be a significant cost associated to vote on blocks, so the proposal is vulnerable to Sybil attacks.