With the popularity of HDTV / movies with the 16:9 resolution, almost all LCD screens you'll find will be at some sort of 16:9 form factor, with 1920x1080 (HD 1080) being the most popular. (I.e. divide the x by the y and the result will equal 16/9 = 1.7 repeating)
The 1600x1200 you speak of is an even older 4:3 config (1600/1200 = 4/3). This "wide screen" fad has changed the monitor form factors from 4:3 to 16:10 (my personal favourite) to 16:9 (TVs).
See:
Display resolution - Wikipedia, the free encyclopedia