I asked Copilot, and yes, I know you should not take that answer as a fact, about how many PC games that require a RT capable card to run without having a rasterized fallback option.
How many games are there?
Two.
One is Metro Exodus Enhanced edition, the other Quake II RTX. Both of these have regular versions that has no RT requirements, so in fact there are NO games that requires raytracing capable cards as of now.
If you can find some examples that Copilot has missed do add them, but I'd be surprised if there are more than a few.
It's all optional, even after about 8 years on the market.
Actually, the newest version of doom does not have a fallback. It requires raytracing.
NVIDIA or AMD hardware Raytracing-capable GPU with 8GB dedicated VRAM or better (examples: NVIDIA RTX 2060 SUPER or better, AMD RX 6600 or better)