The term DOS game
is really something of a misnomer. Games don't
run on operating systems, they run on
hardware, especially video hardware, or on hardware abstraction layers.
When speaking of PC games, it makes more sense to talk about
text mode games,
CGA games,
EGA games,
VGA games, or
SVGA games.
A good many CGA games (Boulder Dash,
Loderunner, the early
Wizardry games)
didn't use DOS at all. They were so-called booters.
They came with an operating system of their own. And even many games that
did use it often bypassed it and accessed the hardware directly. These are
usually the games that don't run in, or even crash, DOSBox. PC games would
be a more correct term. (The boxes of 80s PC games usually read something
like IBM PC/XT/AT and compatibles.
IBM didn't exactly make it easy
for developers.)
Windows games on the other hand should not be seen as a subset of PC games at all. Windows is a hardware abstraction layer, and nearly every version has been available for more than one hardware platform. A Windows 3.1 game will most likely run on NT 3.1 on a DEC AlphaStation as well.
But the term is well established, and there's not much to do about it.
There are currently 517 DOS games for download.