The better coded games out there will happily run at any resolution supported by the driver including the legendary Total Annihilation from 1997.
TA was pretty much the first thing I tried when I got my 24" LCD & it plays just fine at 1920*1200 :)

The not so well coded games even quite recent eg Battlefield2 only support 4:3 resolutions so I have to play at 1600*1200.

Some monitors handle 4:3 by letterboxing (on the sides) while others just stretch the horizontal out.
My monitor stretches 1600*1200 but is optional for other resolutions & while technically 1600*1200 stretched out to 1920*1200 is a distorted picture, in practice I haven't really noticed it in most games.