Hi,
Of course when you are designing your 640x288 layout on a PC screen in another resolution like 1024x768 ,it looks like widescreen format. But when you use the layout in 640x288 you don't really have this impression.
640x288, is a good choice if you want make layout with a list on a side and an snap on the other.
Because most of the game (at least old game) don't have a resolution that exceed about 320x256 , so if you use a 640x288 layout , you could dedicate the half of your screen to the snap or the video and the other to the list. This way the Video or snap will not be streched. Visual quality will be better.
If you chose a resolution like 368x240 , your "snap" zone will be obviouly lot of smaller than the game original resolution and you will loose detail.
BTW what avatar do you have, to me it looks like Gatchaman, though not the 70's version - is it Gatchaman Fighter (a sequel series) or maybe even the 1990's OAV's?
My Avatar is "Actarus, prince of Euphore" the pilot of Goldorak robot . (That 's french names) , i don't know his name in other country, but it is the pilot of "Grandizer" , or "Grendizer" . He appear's in the 3rd part of the Mazinger trilogy. It has been extremly popular in France at the end of 70's .