This article is from the comp.sys.ibm.pc.hardware.video Frequently Asked Questions, by Michael Scott with numerous contributions by others. (v1.0).
There is no right answer to this question, because it is subjective. However, my recommendations are:
Monitor Size Aspect 14" 15" 17" 20" Ratio Screen Addressabilities640x480 4:3 O O G G 800x600 4:3 A O O G 1024x768 4:3 NR A O O 1280x960 4:3 NR NR A O 1280x1024 5:4 NR NR A O 1600x1200 4:3 -- -- NR A 1600x1280 5:4 -- -- NR A
O - Optimal G - Pixels are large enough to appear grainy A - Acceptable NR - Not Recommended - unless you like looking through a magnifying glass
Keep in mind that the aspect ratio can be important. Standard televisions and computer monitors are designed to work with a 4:3 aspect ratio. If you use a 5:4 aspect ratio on a monitor with a 4:3, your screen image will be compressed vertically, making circles appear as ellipses. The error associated with using a pixel addressability aspect ratio of 5:4 with a monitor os 4:3 is about 6%.
 
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