That's the problem, more specifically.
World of Warcraft is pretty old and basic in terms of visual needs, and the other two aren't super demanding either. They may run on your IGP, but I doubt they're doing so at good speed while being at higher settings/resolutions. I, personally, don't consider that "running PC games just fine", but rather, just barely running some mid-range demanding games at basic levels.
Secondly, you're mistaken to compare PC gaming to emulated gaming anyway. The latter will always have far greater needs, even if the emulated system is "far weaker" than the PC itself.
Lastly, the cartoon shader is fun to mess about with, but I wouldn't recommend it for actually making the game look really good, because, well, it doesn't do that (in my own opinion). You're better off just naturally enhancing it, although you aren't going to be able to do even that. You're going to have to stick with software rendering (I'd use pSX, not ePSXe in that case) or, if you'd rather, the Direct3D plug-in.
