25-30 years ago, I'd have been all over some of these - particularly Veil of Darkness and The Summoning. I really liked SSI's games, and these ones were hard to find in the UK (at least for me), so they became almost mythical. Subsequently I've bought copies and been rather underwhelmed. Played at the time of release, they were probably solid mid-tier titles. 30 years later, you'll probably need some fairly rose-tinted spectacles...
Veil of Darkness is probably the pick of the litter, although I'm not qualified to comment on Star General, as I haven't played it, and am not a genre fan. The prices feel a touch steep, and honestly, most would be better remastered/reinvisioned for today's audience.