Dear Student,
Chloroplasts provides sunlight which is an important raw material for photosynthesis. This enable plants to synthesize food by their own. Therefore, they are called autotrophs. So, plants have to spend less energy for their energy requirements and thus, having chloroplasts gives plants cell an advantage over animal cells.
Animals are heterotrophic animals and they do not prepare their own food rather depends on others for their body requirements.
If an animal cell had chloroplast, there is no need to eat food. Due to the presence of chloroplast, they may turned to green colour as chloroplast is a green photosynthetic pigment.
Regards