The expression "first begotten of the dead" has caused much perplexity. Obviously Jesus was not the first one to be resurrected. Besides Moses in the Old Testament, at least three individuals were raised from the dead by Jesus Himself.
There are two ways the word "first" may be understood. It can mean either first in point of time or first in pre-eminence. The President's wife is spoken of as the First Lady--not because she is the first lady who existed, but first in honour and pre-eminence.
Christ was "first begotten of the dead" because that resurrection took the pre-eminence over all other resurrections. In truth, all other resurrections had taken place or would take place by virtue of His triumph over the grave. His power to lay down His life and take it again (John 10:17) set Him apart from all others who had been resurrected. His was first in importance to such a degree that none other ever could have been raised without reference to His resurrection.