Sims 2 Resolution Stuck on 800 x 600

@BunniesAreCute ,while you do need to edit the Graphics Rule.sgr to recognize your graphics card, there are additional lines that need to be edited by hand to be able to have the game recognize the various resolutions. 

SimsVIP (which I am not sure if I can link to due to forum rules) has easy to follow step by step instructions on how to edit the Graphics Rule file to increase the resolution. A Google search for "Sims 2 resolution" should show you the link to SimsVIP and you can follow the instructions from there.

@BunniesAreCuteLook online for SimsNetwork's Graphics Rules Maker which will fix the resolution and some other things that might be causing graphics issues, as well as increase your texture memory to avoid pink flashing. You can let it auto-detect the best settings and use those; just don't disable Sim shadows as there is a mod to fix those (Google Sims 2 shadow fix). Make sure that you run Graphics Rules Maker as Administrator, so it is able to save the changes, and don't forget to add your card to the database.

@BunniesAreCuteDo you get an error? Go to your latest pack folder (I'm guessing Mansion & Garden Stuff if you have Ultimate Collection; C:\Program Files (x86)\Origin Games\The Sims 2 Ultimate Collection\Fun with Pets\SP9\TSData\Res\Config) and see if files were modified.

I would also recommending checking VirtualStore for any leftover files, since Sims 2 files often end up there; an older GraphicsRules.sgr might be there.
Press Win + R and type in %appdata%. You'll end in AppData\Roaming, so go one folder back. Then go to Local\VirtualStore, and you'll see program files folders. Look for Sims 2 files in there (AppData\Local\VirtualStore\Program Files (x86)\) and delete any folders related to it, especially if you find a Graphics Rules file.

@BunniesAreCute , are you sure you edited it? Simply running Graphics Rule maker does not edit all the lines of code that need to be edited to run the game. There are some additional lines that you will need to edit by hand.

My other bit of advise is to go to YouTube and to find videos on how to get Sims 2 to run on Windows 10. Follow those videos, step by step. It is possible to get the game to run, you just need to be patient and to sometimes dig a little deeper into where files may be that are preventing the game from running properly.