If the text is blurry only in the horizontal direction, this points to a graphics card problem. If the blur is both horizontal and vertical this points to the monitor. What is different between text and games pictures is that text is usually a small amount of fine black detail on a white background, whereas games and other pictures are more evenly distributed over the whole tone range. When a monitor gets old the tube cathode often can't supply the amount of current required to light up the whole screen. Increasing the brightness to compensate can result in incorrect voltages to focus the beam. When this happens a new monitor is the only solution.