Why was God displeased with Cain's sacrifice? Was it because Cain didn't sacrifice animals? He could have easily traded his produce for one of Abel's quality animals. Yet, the text doesn't specify that animals were the only sacifice God required at this time. So, his land produce may not have been the issue. A likely reason God wasn't happy with Cain's offering was because Cain didn't offer the best of his wealth and prosperity? Perhaps he offered the second-rate produce to God.
This text, as well as so many others, is dealing with our attitude toward God. Was Abel "more" perfect than Cain? No. But it seems that Abel's worship to God was accepted because he used the best of what he had to offer; thereby, honoring God for who He truly is - the provider of all blessings.
The Lord's humbled . . . John A. Reeves