Sidonnai: I own the original Titan Quest & Immortal Throne discs and the game works perfectly with Intel integrated graphics. The specs quoted by GOG say;
128 MB NVIDIA GeForce 6800 series or ATI Radeon X800 series or equivalent (256MB NVIDIA or AMD card recommended)
Has the graphics requirements been altered so that Intel graphics are no longer supported? Or is GOG just 'following the herd' and ignoring Intel graphics?
"Perfectly" is likely a matter of opinion, but be that as it may...It's never been a case of developers and publisher's "ignoring" Intel graphics--rather the opposite--it is Intel ignoring the ongoing and developing GPU standards to some extent. Intel's GPUs are all "integrated"--that is, designed into the cpu circuitry, as Intel does not make any discrete 3d GPU accelerators like AMD/nVidia. Intel concentrates far more on "business" graphics support (eg., laptops) with only a slight nod to 3d GPU support offered by D3d & Vulkan and supported by nV/AMD in hardware. What often happens with Intel GPUs is that for the sake of saving circuitry and refining their Integrated GPU/CPU production yields, sometimes functions that *ought* to be supported only in hardware under D3d or Vulkan are supported by Intel only in *software*--meaning, by the cpu. Often the result is that the emerging performance taking that route is completely unsatisfactory. That's the ongoing problem with Intel GPUs. For web browsing and spreadsheets and word processing chores Intel GPUs are fine--for 3d gaming, though, Intel is not the choice to make! That's *why* Intel graphics are often not supported in a given game--they simply lack the requisite hardware.
Bottom line, my advice, for what it is worth: if you like to game do so on a desktop as opposed to a laptop, and game with a discrete GPU by either AMD or nVidia. You will be *much* happier with the results when you game--and besides gaming support, there is nothing the Intel GPUs can do otherwise that the AMD/nVidia GPUS cannot do as well or better.