If you want to understand why Otis 40 years since he died is still unmatched as a great soul singer, then this excellent compilation of his lifetime recordings (several released after his untimely death in 1967) will provide the evidence.
The collection is well compiled plus transcribed and the running order over both CDs reflects the man's live shows where the changing of pace from outright rockers (Respect, Security, I can't turn you loose, Satisfaction etc.) to emotionally sung tender ballads where every nuance and pitch is perfect (Try a little tenderness, I've been loving you too long etc) kept the levels high. Steve Cropper's quote that recording with Otis was like going to Church in that he inspired you is well evidenced here.
While there are no live tracks here, the 40 tracks are an effective cross section of all his different styles and so provide an otstanding introduction and deserve the tile "The very best of" - I could not think of a studio track I would wish had been included. In addition the set has an excellent set of liner notes covering Otis's recording history.
If suitably aroused by listening to what is contained here, consider looking for the solo albums (especially "Otis Blue") and the DVD "Otis Remembered" which captures him live in performance at Moneterey and in the UK during the Stax/Volt Revue Tour.