Probably not, because Steam games need Steam, and Steam needs all of the usual operating system guff.

That said in early PC era it was not unheard of that games could have boot sector on the floppy and they basically just bypassed operating system entirely. Because aside of file access MS-DOS didn’t really have much in the way of “operating system services” in modern sense. Especially toward the end of DOS era games came with a bunch of “extensions” (particularly 32 bit memory managers).