Now I'm curious as to what "hot games" you may be thinking of in this instance.
While EGA Trek is thoroughly awesome and highly recommended, I'm pretty sure it was originally shareware. Super Angelo was also shareware; I think the Mario!! you are referring to was a leaked, incomplete version.That said, some games that always were free which I like:
DOS: Arcade Volleyball, 3-D World, Castle Adventure, Star Goose, Bananoid, SIEGE!, Mario!!, Bombs and Bugs, Pong Kombat (for the amusement factor more so than gameplay), EGA Trek (I think it's freeware?)