Civilization for me, it's my nr 2 game of all time to me.
The first time I played Civilization was in 91. I was 17 at the time with one more year of high school to go. A good friend told me about the game and managed to get a copy of it. He didn't have a PC at home himself so came over to my house on a week day to try it out. We copied it to the HDD, started playing and didn't stop until 7AM the next morning. He raced home to have quick breakfast, and I saw him 2 hours later again in class. The game was so good from the get go, there was no time to sleep!
Civilization has caused tons of sleep deprivation, I've played it for years, alone and together with different friends. Just one more turn is the most powerful addictive game play loop there is. The scope of the game was unheard of, start 4,000 BC and lead your civilization into the stars. Or win by defeating everyone else, but going for the science victory was always my preferred strategy. There were so many different ways to play the game, on the world map or random generated maps against up to 7 other civilizations.
I created different game types by hex editing civ.exe, the run-time library compiled in the executable. I mapped out what all the values meant, noted it all down with offsets so I could easily create different versions with more/less growth, higher/lower costs for certain units/advancements and different attributes for opponents. You could change it up from a highly aggressive game to a very cooperative game, a quick game with low costs and abundant resources or a glacial struggle to maintain a civilization on a harsh planet. The Devs recognized the versatility of switching things up and civ 2 had the runtime library all in easily edited config files.
By switching it up the game stayed fresh for years and I beat it many times at the highest difficulty. So many great memories of playing it together behind the keyboard, discussing strategies while waiting for the computer to make its turns. It also taught me a lot about world history and different forms of government. The consequences of nuclear war and global warming.
While I played a pirated version of the first game, I have bought all subsequent versions day 1. The game sprouted other worldly versions as well with Sid Meier's Alpha Centauri and Civilization Beyond Earth. Still waiting now for Alpha Centauri 2. None of the sequels got me as addicted as the first one though, yet that's also a factor of not having that kind of time nor resilience to skipping sleep anymore. Civilization is a game best enjoyed in 6 to 10 hour sessions...
It's brilliant how much depth and strategy Sid Meier managed to put in a game with 320x200 resolution. The UI was amazing as well as the visuals at the time. Everything was clear and easy to over see. I still prefer the straight top down view of the original, playing on a map, like a board game come to life. It also led to buying the actual board game which we played a lot through university.
1991 had plenty other great releases. Monkey Island 2, Another World, Lemmings, Lotus Turbo Challenge 2, Duke Nukem, Wing Commander 2, Falcon 3.0, F117A Stealth Fighter 2, F1 Grand Prix. Lemmings drew all of us behind the PC, solving levels and writing down the level codes as that was the only way to progress, no save game. Lemmings got me into puzzle games which I'm still into. I just bought Cocoon yesterday and started plugging away at Humanity again, which is pretty much Lemmings in 3D with some devious mind bending puzzles.
1991 also released the awesome Chuck Yeager's Air Combat, arcade dog fighting was new to me coming from more realistic flight sims and Chuck Yeager became an instant favorite. The historic missions were fun, great selection of planes and the mission generator was awesome. It remained my favorite dog fighting game for many years, replacing F19 Stealth Fighter as my previous favorite air combat game.
