games come on full screen because they are displaying at a defined resultion, 1280x720 or 1368x768.
Blue ray discs are a conversion from a cinematic release, and therefore are resprentative of the cinematic aspect ratio, if this happens to be so wide that to keep the aspect ratio right there are black bars then there are black bars, if an image was so tall that it needed squashing let to right then you'll have bars on the left and right.
You can probably force the tv to 'fill the sceen' but you'd then have two problems, everyone would look very tall and thin, and circles would not be circular they'd be ellipses, and each line would be represented by 1.x pixels in height, and hence would look a little blurry, i.e not whatHD quality is meant to be. TV's should be set on a 1:1 pixel mapping mode so that 1 digital pixel on the source is 1 pixel on the screen, and not 1 pixel wide and 1.3 pixels tall.