Which is the most accurate English version of the Bhagavat Gita?
There is no most accurate or best version. All translations have some sort of bias. I am posting below some Gita translations that I have read.
Bhagavad Gita Bhasya of Sri Sankaracharya translated by Dr. A. G. Krishna Warrier;
Gita translated by Radhakrishnan
Gita translated by Swami Tapasyananda
Universal Message of the Bhagavad Gita by Swami Ranganathananda