Renders are low quality, help please.

Hello. I am very new to animating and using After Effects.

Recently I have animated a walk cycle. This walk cycle is 1960 px by 1080 px. In After Effects, the animation looks like this. When I render, the animation looks like this.

I want the pixel dimensions to be 480 px by 270 px or similar, while maintaining a bright, clean look as seen in After Effects. How would I achieve this?

I have tried rendering as avi, flv, MPEG, h.264 and adjusting the 'resize quality' setting to high. Could someone please tell me how to set the render options to be 480 px by 270 px while looking clean?

(I have no problem with rendering a high quality 1960 px by 1080 px animation, but this is not appropriate for email or displaying on Facebook. )

Thank you for reading, 
                                 - Anna.