This argument, however, is grievously flawed. In fact, a great number of Trinitarian Christian scholars have long abandoned the notion that Genesis 1:26 implies a plurality of persons in the godhead. Rather, Christian scholars overwhelmingly agree that the plural pronoun in this verse is a reference to God’s ministering angels who were created previously, and the Almighty spoke majestically in the plural, consulting His heavenly court. Let’s read the comments of a number of preeminent Trinitarian Bible scholars on this subject. For example, the evangelical Christian author Gordon J. Wenham, who is no foe of the Trinity and authored a widely respected two-volume commentary on the Book of Genesis, writes on this verse,
Christians have traditionally seen [Genesis 1:26] as adumbrating [foreshadowing] the Trinity. It is now universally admitted that this was not what the plural meant to the original author.1
If you had attended any one of my lectures you would know that the New International Version is hardly a Bible that can be construed as being friendly to Judaism. Yet, the NIV Study Bible also writes in its commentary on Genesis 1:26,
Us . . . Our . . . Our. God speaks as the Creator-king, announcing His crowning work to the members of His heavenly court. (see 3:22; 11:7; Isaiah 6:8; I Kings 22:19-23; Job 15:8; Jeremiah 23:18)2
Charles Caldwell Ryrie, a highly regarded dispensationalist professor of Biblical Studies at the Philadelphia College of Bible and author of the widely read Bible commentary, The Ryrie Study Bible, writes in his short and to-the-point annotation on Genesis 1:26,
Us . . . Our. Plurals of majesty.3
The Liberty Annotated Study Bible, a Bible commentary published by the Reverend Jerry Falwell’s Liberty University, similarly remarks on this verse,
The plural pronoun “Us” is most likely a majestic plural from the standpoint of Hebrew grammar and syntax.4
The 10-volume commentary by Keil and Delitzsch is considered by many to be the most influential exposition on the “Old Testament” in evangelical circles. Yet in its commentary on Genesis 1:26, we find,
The plural “We” was regarded by the fathers and earlier theologians almost unanimously as indicative of the Trinity; modern commentators, on the contrary, regard it either as pluralis majestatis . . . No other explanation is left, therefore, than to regard it as pluralis majestatis . . . .5
http://www.outreachjudaism.org/genesis1-26.html