Recommended sprite drawing resolution

We are currently developping an Android game in 2D. We are quite early in our developpement.

Because of the large variety of Android phones screens, one question we have trouble solving is the resolution of our sprites. At what resolution should we draw our sprites ? Our sprites are detailled images and not pixel art of any form. What kind of resolution will allow them to render efficently on any screen size ?

Thanks for any support on this topic

I use 64x64 sprites for my game development, it looks pretty good on screens from 2in up to 30in; and renders fast