• Doom/Doom II. They somehow lucked the hell out on mechanics, speed of movement, ease of modding etc. John Carmack did us all a massive solid and got the game released under GPL license only four years after it came out. As a result of the incremental improvements enabled by that, the game keeps my interest to this day.
• TIE Fighter. I used to be a massive Star Wars fan, and this game was just the best thing ever for a detail-oriented kid. I memorized the stats of every single ship and for the rest of time was pissed whenever someone got it wrong. The missions truly require you to use your brain and every advantage at your disposal (in-flight map; reinforcements; wingmates; ship characteristics; good tactics). 've'never come across a better flight sim to this day (although the Freespace series comes close).
• Diablo II. I was 15 when this game came out. I rollerbladed all the way across town to buy this game without my parents knowing. The clerk almost didn't sell it to me because he thought I looked too young but in the end he did me a solid. The game was worth it and then some. It consumed the rest of my teenage years. Digital crack.

Games that deserve to be in the top three but don't fit:

• PlanetSide. I still remember being in shock watching a hundred people shoot at each other without massive rubberbanding etc. It totally redefined what was possible in a game. I was obsessed with making loadouts for every situation. TR forever!

• Dark Souls. They totally nailed the feeling of being in some sort of dark fantasy fever dream. So beautiful, and I love how the lore is relevant to how you feel trying to overcome the adversity of the game. First half of the game has some of the best world design I've ever seen.

• World of Warcraft. I flunked out of college because of this game. I think it was worth it.