I tried running the game in windows xp compatibility mode and other solutions but the game kept crashing. What really worked for me and made the game never crash again, was installing DirectX 9.
1) Go to your steam/steamapps/common/spellforce 2 folder. Here you will have a DirectX folder that contains the install.
2) Enter the folder and click DXSETUP.exe . This will install the version 9 of directx on your computer.
3) Now open your steam browser, go to library and find Spellforce 2 in the list.
4) Right click on spellforce 2 and go to Properties > General > (and click on) Set launch options... Here you have to type -d3d9 so you force the game to run with directx 9.
Now the game will run with directx9 and you'll stop having problems.

To have a higher resolution in the game, you'll have to edit a config file.

1) Find the "SpellForce2" folder in your documents folder (for windows 7 go to users/user/my documents/SpellForce2)
2)Open the document and right click on config.xml.
3)Click edit and select a program like notepad or wordpad.
4)The file contains something like <?xml version="1.0" encoding="utf-8" ?>
<application screenrefresh="0" maxshader="0" screenheight="1080" screenwidth="2560" simd="1" ...
You have to edit your desired resolution here. Set your screen height and width with your resolution like this: screenheight="1080" screenwidth="1920" (if you want 1920x1080)
5)Save the file and exit.

Setting and using a higher resolution will make the camera in the game be very close to the ground. This is really bad and annoying in a strategy game.
The game will let you scroll and zoom your camera only a very little. You'll have to use the console to scroll out farther.
1) Open the game console by pressing Ctrl + ]
(open the console while in the actual game, not in the menu)
2)Type the following command UI:SetCameraFOV(1.15)
The command is case sensitive so type it exactly like this.
For 1920x1080 i recommend the value 1.15, for 2560x1080 the value 1.3.
I'm playing on a 2560x1080 and i like being zoomed out very far away so i'm using the command like this UI:SetCameraFOV(1.5)
You'll have to type this command everytime you open your game, but don't worry the command will be saved, and the next time you open your game and console just press the DOWN ARROW on your keyboard to bring up the command.