Below is a list calculated by profit per hour regardless of level of the 10 most profitable crops. You will not be able to take advantage of this information until you reach level 19 when you unlock Grapes.

1. Asparagus

2. Onion

3. Sugar Cane

4. Peas

5. Tomatoes

6. Green Tea

7. Grapes

8. Sunflowers

9. Ghost Chili

10. Acorn Squash