I can recite a few of these from memory, because you just hear them so often...
Some of the most meaningful to me were the ones coming from a place of spiritual philosophy. I am absolutely not a religious man, nor would I consider myself to be even remotely spiritual or superstitious. That said, there is a sort of poetic beauty through the concept of a deity as a storytelling mechanism, or a way to put a complex philosophy into a memorable narrative.
"Companions, the creator seeks, and not corpses, nor herds or believers. Fellow creators the creator seeks-- those who inscribe new values on new tablets. Companions the creator seeks, and fellow harvesters; for everything about him is ripe for the harvest. ... Fellow creators, Zarathustra seeks, fellow harvesters and celebrants... What are herds and shepherds and corpses to him!" (this quote is is often shortened, but this adaptation is the most meaningful to me)
"Men, in their arrogance claim to understand the nature of creation, and devise elaborate theories to describe its behavior. But they always discover in the end that God was quite a bit more clever than they thought."
I'm not a religious man, but I do identify with the visceral rejection of humanity's collective hubris.
and of course, hearing 'Eternity lies ahead, and behind. Have you drunk your fill?' some 20x per game really cements that phrase into my head.
I frequently play as Zakharov, and I like his quotes, but they're always rambling and difficult to recall in the moment.
That said, anyone playing as University would always make the Hunter-Seeker Algorithm a top priority. Fusion power and orbital spaceflight follow soon after, and that's the game. I usually go after Yang, then the Believers. Pretty formulaic at this point, but I enjoy it about as much, perhaps maybe even more, than Beyond Earth. SMAC just has so much character to it.