Definitely the video card. Most games today rely on that and your CPU is still pretty good despite its age.
Assuming your monitor is a mainstream one, i.e. 1920 x 1080 @ 60 Hz, an Nvidia GTX 1660 should run most games at max or close. An AMD RX 580 comes close for a lower price but is starting to age. Higher priced cards would require quite a lot more from the rest of your system.