In Genesis 4, Eve gives an explanation for naming her first son. Upon careful inspection, the text doesn't say that she gave Abel the same attention.
In the first 2 verses, I think we're meant to understand that Eve favored Cain. Perhaps she believed the Promise of Blessing in the instruction to "be fruitful and multiply" was about this first son.
Adam made love to his wife Eve, and she became pregnant and gave birth to Cain. She said, “With the help of the Lord I have brought forth a man.”
Later she gave birth to his brother Abel.
Genesis 4:1-2 (NIV)