No, YOU cannot be justifiably angry or disappointed in him because he is a fictional character. You cannot love him. Of course it is completely different with God and us. We are real and God really does love us. That makes all the difference. God HATES sin, and even when He knows it is coming from us, He is still angered by it. As Dr. E. said, "God's anger is righteous". It does not have the flaws that our anger so typically does. God's anger is a good thing.
As for the allusion to God repenting for creating man, do you think God "repented"? I don't. If God repented, then that would mean He changed His mind. That would make Him mutable, and I was sure that the Orthodox strongly hold that God is immutable.
If you freely and willingly allow something, even if you hate it, there is no reason for anger. Such anger could only be directed as yourself, for allowing things you hate to happen.
As for the allusion to God repenting for creating man, do you think God "repented"? I don't
In Gen 6:6 the various English translations say that God "repented," "grieved," or was "sorry" for having created man.
In Gen 6:7 the Lord is actually quoted as saying that it "repented" (KJV) Him, that He was "sorry" (NAB) or that he is "grieved" (NIV) for creating man. The Septuagint (LXX) says "angered" or "enraged" (ethumothen)
Of course Numbers 23:19 says "God is not a man that He should lie, nor a son of man that He should repent [LXX says "be threatened"]..."
When in doubt, drop the verses that don't fit the pre-fab image, right? In one it says God was sorry; the other says God cannot be sorry.
So, let' assume then that they really mean "angry," and we have much of God's anger in the OT. Looking at it from this POV as you like to say, clearly, God was angry for having created us; even just in His anger because He hates our sin. But, honestly, there is no reason even for His anger, even if there is reason for hating our sin.
If someone is in charge and he allows things he hates to go on, the only justifiable anger would be against oneself for allowing it, especially if allowing it with absolutely certain foreknowledge of the consequences of which he is the author.