I'm on an old Windows 8 computer with a dual-core processor and I can play most porn games. However, there are occasional games that older computers can't handle.*
It all depends on two factors.
* The first is the game itself and its engine. If it's RenPy or RPGM or the like, then they're not demanding.
* The second factor is the presence of animations in the game. Now most games have them and they are demanding.
PCs with 4x4 CPU and 8Gb of RAM + SSD will close your problem for heavy gaming, on the built-in video core. A more or less advanced 3D game will require a graphics card.
For simple 2d will go: CPU 2x2 / 2x4 + 4Gb/6GB mem + hdd / ssd even in built-in video core