Every time I launch the game I need to select what resolution and color depth I want to play in, why do I have to do this every single time I launch the game?. Is there a command-line option to permanently set these things?.

The start screen cannot be bypassed completely but you can set the default values to be constant. It does require a registry edit though. The entry's location is dependant on operating system and compatibility settings. Ask if you need more details.

The resolution gets saved but I have to select 32-bit color depth every time I load the game. I've edited the registry under "HKEY_LOCAL_MACHINE\SOFTWARE\Crystal Dynamics\Legacy of Kain: Soul Reaver\1.00.000", and modified "ScreenDepth", changing the value to 20 instead of the default 10, but it still defaults to 16-bit color depth when I launch the games shortcut. I'm running Windows Vista 32-bit by the way.

In the registry I also tried changing Vsync to "0", but it resets every time you start the game.

Try searching for another entry. For some reason on my Windows 7 64b Pro I have 3 separate nearly identical entries and in my case the one relating to VirtualStore works (HKEY_CURRENT_USER\Software\Classes\VirtualStore\MACHINE\SOFTWARE\Wow6432Node\Crystal Dynamics\Legacy of Kain: Soul Reaver\1.00.000 (but that's a 64 bit system thing)) and Local_Machine one is always ignored unless I run the game as Administrator.
I also think that Vsync is hard-coded and that setting doesn't really work anyway.

There are no other entries like the one found under "HKEY_LOCAL_MACHINE\SOFTWARE\Crystal Dynamics\Legacy of Kain: Soul Reaver\1.00.000", I've looked previously.
I'd probably have to edit the "kain2.exe" with an hex editor, it's most likely hard coded so I'm not gonna let it bother me and just live with the way it is.

I do run the game as administrator, even though I'm the only user of this pc, and have the game installed into the default directory of "C:\GOG Games\Legacy of Kain Soul Reaver". The game by default runs in "Windows XP (SP2)" compatibility mode, and "Disable display scaling on high DPI settings" is enabled.

I thank you for the help Paradoks, cheers!.

It's definitely not hard coded as it respects the settings for me on both Win 7 64 b and Win XP. Then you can experiment with different settings like not running as Administrator and removing Win XP compatibility (and then checking whether there are new entries in the registry). That's how I run it and I've noticed no difference in game with these settings.

If you answer a 9 month old thread saying there is an easy solution, it would be polite to say what said solution is. Good luck finding Wow6432Node on a 32 bit Windows XP.

Then what is the damned fix?