I use Win Vista Home Premium 64bit.
I found and located "game.cfg" for Crysis 2 in "Saved games" folder.
Adjust from there for custom resolution to take affect. The commandline is already there so just change the numbers.
Trying to adjust the resolution from Console, System.cfg & autoexec.cfg WILL NOT work.
Also two very important steps.
1) If you use custom graphics in "autoexec.cfg" make sure you erase the the commandline "sys_spec #" in "game.cfg" file otherwise your settings will be reverted back to default.
2) Make "game.cfg" file "Read-only" otherwise your custom resolution will be reset to default too.

Please feel free to make feedback and let me know how you did.

Attachments:

Custom resolution.jpg [ 54.8 KiB | Viewed 86 times ]

C2 game.cfg location.jpg [ 64.86 KiB | Viewed 86 times ]

Thank you so much VJLin!
I've been trying to change my resolution lower ever since I bought the game. I contacted EA support and they did not want to hear what I wanted to say. They just said you are not meant to change beyond the given resolutions. When in 800 x 600 I only get 20 FPS..... Not playable.
I have a low spec laptop so now with 640 x 480 I can play Crysis 2 with no lags @ 35 - 40 FPS!