If you see that an art asset pack has been used for many other games, are you more or less likely to want to use the art for your own projects? Why or why not?

I've considered showcasing games that use my art, but I don't want to deter people from actually using it

Yes, but more so because they tend to clash in style, not because it’s used somewhere else.

Otherwise, I use third-party art all the time, e.g. OpenGameArt.

It depends. I would never use anything in the Brackey's Platformer assets pack, but that's simply because it's used so often. Pizzadoggy doesn't seem to have any problems with selling assets with a gallery of projects using them. I would use pretty much any other assets, but just as long as it's not used too often.

I mostly don't use art packs because I have a big ego and can't stand the sight of something I didn't make.

It depends on the art type.

If the art asset pack is for sprites or effects or anything player would focus on, I would less likely use the pack.

However if the asset pack is for background or back layer, I could reuse it.