Despite being a PC gamer for well over a decade, mods are almost completely worthless to me.
They are not a selling point in any way.
That said, there have been a couple of useful mods in the years:
- Warcraft 3 Tower Defense mod got me into TD games.
- UI convenience mods are nice. I use one for Dragon Age 2 that toggles items so you don't have to run around holding down the shift key (or whatever it was).