So I have more than 30 computer monitors that came from auction batches that I purchased for resale, and I'm considering keeping one of them to replace the CRT monitor from 1999 I currently use. Dells, Samsungs, Acers, and HPs. I know there are pros and cons to CRTs and LCDs, especially for gaming, does anyone have a personal preference for the purposes of The Sims 2?

If you can set the game to the native resolution of your flat LCD monitor, then it will look good. Sometimes the native resolution is not easily accessible on monitors that are sold as TVs. A really big monitor may need more power than the computer has to drive at the native resolution.

The appeal of CRT monitors is with older games that only offer one or a few lower resolution options. This causes upsampling, which makes sparkly things like gemstones dull. Such things occur mainly with hand-drawn assets instead of 3D, which always get stretched out. A CRT can, within limits, smoothly adjust the pitch between lines instead of matching fixed pixels.

CRT monitors have a low life expectancy. I would save them for retro gaming.

I have always used an LCD monitor with TS2 and it looks and runs just fine. The details are sharp and crisp as they should be. TS2 actually supports up to 1080p (aka "FHD"). There is little reason to use a CRT monitor nowadays except for nostalgia feels. If you do run an LCD monitor, you'll very likely need widescreen patches for the UI to be adjusted to the higher display resolution properly. But it's a small thing that shouldn't discourage you from upgrading.