I suspect such graphics were unachievable in 1991. Even if they were it was a different time for games. The shiny look we have nowadays is meant to appeal to kids and casual gamers. Back then computers -- and by extension computer games -- were much less available and mostly an adult thing. What civ had that tabletop games can never have is sleekness: the rules, the dice, the card draws are all under the hood. Structured data is presented to the player at the press of a button. And you don't even need other people to play it, which makes it faster. The AI's all even have personalities (as much as you can fit a personality in several bytes).