Can we even begin to imagine how wonderful life was for Adam and Eve? Ever wondered how long they lived in the garden before the fall?

Why was Abel’s offering more pleasing to God than Cain’s offering? Could it be because of the attitude of the giver? Did Cain give his best? Cain brought some of the fruits of the soil. But, (implying a contrast) Abel brought fat portions from the firstborn of the flock. Abel's offering required the killing of an animal demonstrating that he was bringing more than just an offering, he was bringing a sacrifice. Abel knew that he needed forgiveness of his sins, and that could only come with the blood of an animal sacrifice.
Hebrews 9:22
In fact, the law requires that nearly everything be cleansed with blood, and without the shedding of blood there is no forgiveness.

Could it be that Cain had so sense of sin or need of atonement? Did he think he didn't need to be forgiven.

Gen 4:7
If you do what is right, will you not be accepted? But if you do not do what is right, sin is crouching at your door; it desires to have you, but you must master it."

Just as Satan tempted Eve, he is crouching at our door waiting to tempt us as well.

1 Pet 5:8
Be self-controlled and alert. Your enemy the devil prowls around like a roaring lion looking for someone to devour.

Notice the ages of the people listed in the genealogies. Why did people live so long before the flood? See the Creation study on the website at www.philandpatti.com. It explains all about the protective canopy that allowed people to have longer and healthier lives.