[gavanwoolery]

Master of Orion was notable in that it was the first game I remember with "meaningful" NPC interactions. Even though interactions were quite limited (make/break alliances, espionage, trade, etc), early alliances could determine the final outcome of the game. But more importantly, it felt emotionally compelling. I found myself getting angry at certain factions when they spied/voted/etc against me. They also took the time to illustrate dispositions IIRC, so you could see when a race was happy or angry with you.

[hikarudo]

Some twenty years ago, while playing Master of Orion, I asked the Humans to ally with me and go to war against the most powerful race. They replied something like: "Yes, we will be your allies. We fondly remember when you gave us +10 Terraforming."... which had happened scores of turns earlier, when in desperation I bribed them with tech so they wouldn't attack me!

[aidenn0]

A neat little experiment in meaningful NPC interactions was Siboot[1]. The DOS version is probably available somewhere. It's rock-paper-scissors with a social element. Well worth at least an evening's play. The author has released the mac source-code, but good luck building it. The DOS version is available at various abandonware sites and that's probably the easiest way to play it.

1: https://en.wikipedia.org/wiki/Trust_%26_Betrayal:_The_Legacy...