Just about any space sim possible (I still can find some old registered versions of shareware titles, like gamma wing, recently preserved from 1994).
However, aside from the big guys (the wing commanders and xwing saga), those I also hugely like are:
EPIC (digital image design), a true wing commander contestant and doing a very good job at storytelling, AND mixing for the very first time space and atmospheric missions in one game (some say that WC3 will have used the idea from there).
INFERNO: the odyssey continues. sequel to epic: a true work of art I couldn't even describe! Try googling it or better still secure a copy.
And other oddities (I very much like psygnosis productions) like pyrotechnica, darker, or even a very fun tank game called assault rigs.
Of course terminal velocity along with their spiritual sequels (even though not dos based): fury3, it's add on f-zone (I could never figure out how the level editor included worked as my copy came without instructions), and hellbender.
and many others I couldn't even begin to list (including a lot of rarities very few persons have seen).