A true classic, anyone that played it at the time will tell you stories of how they struggled against hidden aliens, panicked soldiers and night-time terror missions. The difficulty made the victories all the sweeter though, and the real fightback begins when you research the alien technology and turn their weapons against them.
The game spawned a few sequels, beginning with the underwater-based Terror From The Deep and ending with the disappointingly poor Enforcer in 2001. It had seemed the franchise was dead, and strategy games in general were out of favour, although a few other developers did have a go at capturing the magic, with varying success. More recently though, the franchise was brought back from the dead, with the new XCOM: Enemy Unknown by Firaxis (most famously the team behind the recent Civilization games).
A new XCOM game brings mixed emotions for me, as with every attempt to replicate the games of my youth. For every positive experience, there are usually a few terrible examples. Sometimes the "remake" or "reboot" can completely change the core gameplay, as seen most recently with Syndicate.
But it's not all bad news, and sometimes even though a new game can be different from it's ancestor, a great game can still be made. I believe, for all it's faults, that XCOM is a great game. I've certainly enjoyed it, and while it may have taken me some time to get used to it's new systems and interface, it has been a worthy addition to the franchise.
I'm still yet to finish XCOM, so I'll hold off on a more in-depth judgement, but I will be playing UFO: Enemy Unknown again, to enable me to compare and contrast a bit better. UFO is often a slow, tactical game that rewards patience, and it's one that I can't even remember completing (I think my brother might have, which is where my memories of the final mission come from). So I'm hoping to complete both XCOM and UFO for the first time, and see which one comes out on top!