Yes, it's the best videogame of all times.
Anyway, SMAC is a strategy game where you rule a human faction, landed on an alien world, and struggle to survive: you'll have to fight the Alien lifeforms and at the same time compete with the other factions for supremacy on this brave new world. ;-)
SMAC got perfectly balanced factions, got a unit editor that will let you create the wildest weapon projects, got countless city improvements that will improve your faction.
But please, don't look at SMAC like any other "strategy game": it is much much much more.
It's a piece of digital art where you will face ethic decisions on a daily basis: will you try to exterminate the Alien menace or will you try to coexist, or even merge the human genome with them and create a new step in human evolution? will you accept to nerve stapling your own citizens so riots won't happen again in your dystopian cities? will you run a democratic government or force a dictatorship?
SMAC could even change your views about various topics like life, philosophy and God.
I heard SMAC costs a lot now at the online auctions: well, believe me, it worth every single cent.
So go and buy it, and once you got it don't let it take dust on your home shelves.
Play it, and let your wife play it, and your sons, your friends, your husband, your father, your neighborhoods, your work collagues.
Make them all see and realise how a high level of art a videogame can reach.