I was annoyed with that fact that Versus only has a handful of preset resolutions and none for those of us with widescreen monitors, so I set out find a solution for this. After a bit of tinkering, I've found a way to play Versus at any resolution you please!
Keep in mind, this method *does* stretch the image. This 'fix' mostly exists simply for a more comfortable playing experience without black bars on the sides of the screen and/or the flickering while switching between resolutions.
This method has only been tested on Windows 7. Other operating systems such as Windows XP and so on may have the ProgramData files we need to work with in a different folder, so you may have to search for the proper folder 'address'.
1) Navigate to 'X:\ProgramData\Ubisoft\Tom Clancy's Splinter Cell Chaos Theory'.
2) Open 'SplinterCell3.ini' in Notepad.
3) Scroll down (or use the Find function) to the '[LauncherResolutions]' category. These are Versus' preset resolutions.
4) Change the the 1600x1200 in the res5=1600x1200 line to your desired resolution. For example, I use 1680x1050, so I would change the line to res5=1680x1050.
5) Save the file. Close Notepad. Set the SplinterCell3.ini file to 'Read Only'.
6) Navigate to 'X:\ProgramData\Ubisoft\Tom Clancy's Splinter Cell Chaos Theory\Saved Games\Versus'
7) Inside this folder, you should find a file called 'USERNAME_prf.ini'. USERNAME would be replaced by whatever you named your initial profile in Versus. In my case, my file is called 'EdisLeado_prf.ini'.
8) Look for the line ScreenRes=X, replace X with the res line number you changed to your desired resolution. Since I'm going to be using the resolution in the res5 line in the SplinterCell3.ini, we'll change X to 5. So, the line should read ScreenRes=5.
9) Save the file. Close Notepad. Set 'USERNAME_prf.ini' to 'Read Only'.
10) Almost done! Navigate to your Splinter Cell Chaos Theory Versus System folder, in my case it is X:\Program Files (x86)\Ubisoft\Tom Clancy's Splinter Cell Chaos Theory\Versus\System.
11) Open up the 'Default.ini' file in Notepad.
Scroll down (or use the Find function) to the '[WinDrv.WindowsClient]' category. Find the lines 'FullscreenViewportX' and 'FullscreenViewportY' and replace their numbers with the resolution numbers you set previously. In my case, I would set 'FullscreenViewportX' to 1680 and 'FullscreenViewportY' to 1050'.
12) Once again, save the file. Close Notepad. Set the 'Default.ini' file to 'Read Only'.
13) Launch the game however you do it (through 3D-Analyze or simply by clicking the regular .EXE). Login to a profile and go into the Profile Settings and Video Settings menu. Make sure the 'Resolution' is set to the resolution you 'replaced'. In my case, I replaced the 1600x1200 resolution in the .INIs, so be sure to set it to that in-game. Accept the resolution, then back out of the menus and restart the game.
There you have it! You can play Versus at whatever resolution you want! While everyone appears short and fat at the resolution of 1680x1050, at least there's no wasted space on my monitor and no annoying flickering when the game changes between resolutions. Have fun!