In this moment i'm very confused with all...

Helm, You say, not understand why I o why any pixel-artist want make perfect circles ¿?
Is correct you thinks this ¿? And if this is correct, how you make a circles? pixel-at-pixel ¿? and if you need to make a isometric circle of 200x200 with only 1 pixel and without AA, you make pixel-at-pixel?
I think first you need create a "perfect" circle or good circle and with PSP make Skew 26,656 and you have this:

And after you retouch pixel-at-pixel....
Well, I for make an isometric circle i need 2 perfect circles(if i not have a perfect circles the result will be incorrect) and i make this:
http://videotuts.webcindario.com/videotutos/videotut7/isometric_circle_paint_matriax.htmlAnd for the tutorial of the "ball"... the tutorial is not for make a simple ball, first make a example of ball and for make this i find the problem to create perfect circles.... and after when you have a ball etc.. i explain how to texturize, etc...
And when the tutorial is finished you should know make this:

For you is possible make this is very simple(viewing you avatar i think you are a very good pixel-artist), but for me and for the people not have idea about pixel-art or are learning in this moment, i think this can help.
But if a pixel-artist how you say this.. i not continue with the tutorial.