The gospels to which you refer are not of equal value,
so your question cannot be answered generally. All of them are later
works that were not incorporated into the official canon of Scripture
for a variety of reasons, not all of which we will ever know.
Perhaps it was because they were later in history. Perhaps it was
that they were not judged as authentic. Perhaps they were caught up in
early church struggles and wound up on the losing side.

The thing we gain from them is a vision of early
Christian history that is different from the orthodox view with which
most of us were raised. It also confirms the recent scholarship that
has successfully challenged ecclesiastical propaganda, that in the
beginning of the Christian era there was not a single Christianity,
but a variety of Christianities that were competing with one another.
The gospels to which you refer reflect that early variety.

The Gospel of Mary, the mother of Jesus, is not thought
of very highly. I am always suspicious of "lost" gospels and can find
very little about it except in circles of Catholic piety. Surely it
is not authentic and we have no record of the mother of Jesus writing
anything and surely she was not alive when this second century work
was written.

The Gospel of Mary Magdalene has been treated in a book
by Karen King of the Harvard Divinity School, who found great meaning
in that work.

The Gospel of Judas has been treated in a book by Bart
Ehrman of the University of North Carolina, who is one of the great
scholars in early church history.

The Gospel of Thomas is treated with great respect by
the scholars of the Jesus Seminar, who actually elevated it into the
Canon in the book edited by Robert Funk called The Five Gospels.
Elaine Pagels at Princeton has done what I regard as the best work
on the Gospel of Thomas in her book Beyond Belief.

I commend all of them to you for your study. Having
said that, however, I do not feel any great desire to take much time
to study these late sources, since I do not believe that they contain
much that is worthy of serious scholarly attention. The Gospel of
Thomas would be the only exception to this statement. I am not
nearly as impressed with these works as some of my colleagues seem to
be. Time will tell who is correct. I am willing to be convinced, but
that has not yet happened.

John Shelby Spong