Genesis 1:31 – "God saw all that he made, and it was very good."
Genesis 6:6 – "The Lord was grieved that he had made man on earth, and his heart was filled with pain."
These two scriptures may appear contradictory at first when read without observing the larger context. The discrepency can be solved quickly when we notice what happened in the course of the history of man in between the times when these two statements by God were made.
Genesis 1:31 records the status immediately after God had finished all his creative work, and indeed "it was very good". Now then, sometime after this, a drastic change occurred in connection with the sin of Adam and the fall of man, which is recorded in Genesis 3. Sin and death entered into the world due to Adam's sin (cp. Romans 5:12). By the time of Genesis 6, sin had had its influence on mankind and it is recorded in Genesis 6:5: "And God saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually." Thus a drastic change had occurred.
When it then is stated that it grieved God that he had made man on earth, we must notice that God was not grieved at the original state of affairs and what He actually had made, but rather at the situation and what had become of man due to man's disobedient and wicked doings after Adam's sin.
The statements made by God are not regarding an identical situation, but are regarding two different situations, involving man in two different states of affairs.