Importing texture without losing its quality for mobile devices

Hi, When i import .png landscape images to unity with 1024x1024 or 2048x2048 its displaying fine without losing its original quality, but when i importing landscape images with 1024x768 size (original size) it pixelating and lose its quality. I am working it for mobile device (iOS/Android), what is the best way to import png images without losing its quality and in a compressed format which will support and run smoothly in mobile devices.

Thanks in advance, Ben

Read through Import Settings related to your Texture type, and take a close look at filter mode.