Structures don't look good on screen.
First, check to make sure you are using the latest display drivers for your hardware. Next, it could be that what you are seeing is a limitation of the resolution a screen can display, especially if it prints ok. A screen can display at 72 dpi where a printer can output at much higher resolutions. A workaround to getting higher resolution structures on screen is to save your structure as a TIFF file. If you save as TIFF (ChemDraw Pro 4.5 or higher required), you can set the resolution in the Save As dialog box. A high resolution TIFF will get you the high resolution on screen that you need.