I sqw and I tried this suggestion on PISTACHIO BRAINSTORMIN* on how to make a good and adaptive screen ration. For every different screen size, let's say I put the perfect circle as a Texture in LibGDX and played it on screen. Here's the blueberry image example and it's perfectly rounded:

When I played it on the Google Nexus 7, the circle turn into a slightly oblonng shape, resembling as it was being flatten a bit. Please observe this snapshot below and you can see the blueberry is almost but slightly not perfectly rounded:

Now, when I tried the suggested code for aspect ratio, the perfect circle retained but another problem is occured. The problem is that I expecting for a view on center but instead it's been moved to the right offset leaving with a half black screen. This would be look like this:

Here is my code using the suggested screen aspect ratio code:

Class' Field

// Ingredients Needed for Screen Aspect Ratio
private static final int VIRTUAL_WIDTH = 720;
private static final int VIRTUAL_HEIGHT = 1280;
private static final float ASPECT_RATIO = ((float) VIRTUAL_WIDTH)/((float) VIRTUAL_HEIGHT);
private Camera Mother_Camera;
private Rectangle Viewport;

render()

    // Camera updating...
    Mother_Camera.update();
    Mother_Camera.apply(Gdx.gl10);

    // Reseting viewport...
    Gdx.gl.glViewport((int) Viewport.x, (int) Viewport.y, (int) Viewport.width, (int) Viewport.height);

    // Clear previous frame.
    Gdx.gl.glClearColor(0, 0, 0, 1);
    Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);

show()

        Mother_Camera = new OrthographicCamera(VIRTUAL_WIDTH, VIRTUAL_HEIGHT);

Was this code useful for screen aspect ratio-proportion fixing or it is statically dependent on actual device's width and height?

*see http://blog.acamara.es/2012/02/05/keep-screen-aspect-ratio-with-different-resolutions-using-libgdx/#comment-317