What is the most accurate Bible version?
I have begun such research and fieldtesting and the results for accuracy of Bible version can be found on my webpage with Studies evaluating English Bible versions. But that is only beginning research. Final results will likely differ from the relative degrees of accuracy which my studies have shown so far. The results of my studies are also surely influenced by the particular Bible passages I chose to evaluate. My regular translation work does not allow me the massive amount of time required to do the verse-by-verse analysis and fieldtesting necessary for a truly thorough evaluation of accuracy in English Bible versions.
Although the claim is often promoted that literal translations are more accurate than idiomatic translations, that claim is easily disproven by examples where literal translations of figurative expressions in the biblical text do not accurately communicate the original figurative meanings to intended translation audiences. We have had a number of posts on this blog which demonstrate clearly, in my opinion, where a literal translation of original figurative language is not accurate for its intended audience. My preceding post on "heavy ears" was one such post.
Exegetes frequently point out what they consider exegetical errors--which is a form of inaccuracy--in more idiomatic translations such as the TEV, CEV, and NCV. (The Message is in a class of its own here; I don't think it can be directly compared with "regular" translations.) On the whole, idiomatic versions translate the figurative language of the Bible more accurately than do literal or essentially literal translations. But they, like any translation, literal or otherwise, have translation wordings which are questioned by exegetes.
Until and if the detailed verse-by-verse exegetical research is done with various English Bible versions, and until and if the necessary verse-by-verse fieldtesting is done among intended target audiences, I don't think we can objectively state what is the most accurate English Bible version. We can, however, I believe, trust that most Bible versions have a high level of accuracy, with the exception of a handful which have been criticised for taking too many liberties with non-consensus exegetical options in translation. One such version that comes to my mind is the Living Bible, interestingly, one of the Bible versions which helped millions of people clearly understand the basic message of the Bible in ways they had never understood before.
We English speakers are rich with Bible versions. Each can be improved. But if you like the quality of English in a Bible version and you believe you understand what that version is saying (we sometimes don't when we think we do), you can usually be confident that you are accurately reading God's Word in English.