The Legend of Zelda series (1992-2006). Most notably, Ocarina of Time and Twilight Princess. As for why these two...
Ocarina of Time was the first video game I ever owned and although it took a few years to grow on me, I'd end up falling head over heels in love with it. The land of Hyrule was unlike anything I had ever experienced. Every room, town, dungeon and region seemed to be brimming with creativity and life; it felt dynamic and vital in a way I never thought games could be. In many ways, Ocarina of Time's Hyrule was designed to be the fantasy world every 10-year old wanted to escape to as can be seen through it's perfect balancing of action, adventure, whimsy and menace. Yet, despite all the monster slaying and dungeon exploring, Hyrule was never so threatening that it wouldn't be a place a child would want to actually live in. Locales such as the lush Korkri Forest to the vast and all consuming Desert Colossus were highly evocative and gave a real sense of place to the imagined world of Hyrule. Ocarina's plot and characters were simple and fairly archetypal, yet no piece of fiction has stuck to me quite like it has. In many ways, Ocarina of Time was my introduction not just to video games but to fantasy fiction and it's related genres more broadly. I remember fondly how my love of the game followed me even when I turned the game off. I would often "play" Zelda with friends at school, trade stories and tips at recess, and write stories and draw pictures about the imagined Hyrule adventures I'd day dream of for creative assignments or at home. Zelda was always on my mind. However, if it weren't for the amazing world design, tight art direction, instantly memorable score intimately tied to it's world, simple characters, devious dungeon design and ingenious progression system, I doubt those childhood memories would be there. Ocarina of Time not only made me a die hard Zelda fan at 8 years old, it also solidified my love of games and probably fiction more generally.
Twilight Princess on the other hand is nostalgic for many other reasons. As previously established, The Legend of Zelda series consumed my childhood and stimulated my imagination; as I often would my daydream about my perfect Hyrule adventure. The boss fights would be bigger, the locales more exotic and memorable, and the quest long and exhausting. I would battle Orc's on horseback and traverse lands unlike any seen before. Both Majora's Mask and Wind Waker were released, but neither would scratch that itch quite like Ocarina of Time did. Then it happened. In 2004, Nintendo unveiled what would be known as "Twilight Princess" to the world. I was ecstatic. I was hyped more than I have ever (and will ever) be for a work of fiction. The decision to make a game that looked to be the spiritual sequel to Ocarina of Time completely enraptured me. I remember coming home from school and spending hours scouring my dial up internet for new information and rewatching the debut trailer over and over. I would go an Zelda fan forums and speculate about what would be in the new game. I'd soak up screen shots from issues of EGM and Nintendo Power for hours. I needed this game.
However, as time went on and Twilight Princess was no where to be seen, I started to drift away from gaming and focused on other hobbies and aspects of life that come with being a young teenager. However, on Christmas '06 I would receive a gift that would change all that: a neatly wrapped package with "The Legend of Zelda: Twilight Princess" enclosed. I didn't even need to open it. I knew what it was. After all these years, it was finally there. I was brimming with excitement to return to Hyrule once more. I quickly loaded it into my Gamecube and got lost in Hyrule all over again.It felt like the kind of Christmas I had as a child getting Ocarina for the first time. Everything about this game is exactly what I wanted from a Zelda title growing up: the sense of adventure, the larger than life boss battles, the many different locations you must traverse through and people you meet across your quest - it was all there. It satisfied both the child in me who had been waiting half a decade for a return to the heroic fantasy land of Hyrule while also appealing to my teenage self whose tastes were drawn to the darker aesthetic design of the game, creative level design and the subtle comforts that an OOT-inspired Zelda now provided. It blended the familiar and the new so astoundingly well; providing an experience both comfortingly familiar and excitingly new.
Perhaps Twilight Princess' greatest strength is how well it embodies a consistent adventurous tone. While it may be structurally linear compared to the NES original and it's previous incarnation, the Wind Waker, Twilight Princess succeeds in making the player really feel as if they are off on a great adventure; guiding the players from a small farming village to the literals ends of the earth in the forms of snow mountains, desert wastelands and even ancient sky-bound civilizations and alternate dimensions. I had a good friend who shared many of the same fond Zelda-centric memories as I who, upon my non-stop gushing, went out and a bought a Gamecube and a copy of the game for himself. Every night, we'd meet up online to rave about the game, compare progress and share stories of any cool secrets we had found - it felt just like those playground talks that used to accompany A Link to the Past, Ocarina of Time and Wind Waker all those years ago. In a way, playing Twilight Princess was an almost symbolic act. I played it during the middle of my teenage years, as childhood was coming to and end and adulthood was on the horizon. Playing Twilight Princess for the first time gave me a reason to revist the things I loved so dearly about my childhood and a chance to say goodbye. To this day, I hold my memories of this game in the same esteem to those of my earlier experiences with Ocarina of Time. I doubt any work of fiction (film, literature, game, etc) will ever have the sort of resonance that The Legend of Zelda series had on my childhood. In fact, it's become a sort of family tradition for my younger sister and I to replay a different Zelda title every year around Christmas, with Ocarina of Time and Twilight Princess serving as annual favorites. Both of these titles are just nostalgic as hell for me and are touchstone pieces of my early adolescence.
However, my non-Zelda/nostalgia answer would likely be either Shadow of the Colossus, The Last of Us or Beyond Good and Evil because they are three beautiful, thoughtful and atmospheric games with distinctive art directions, mature storytelling and distinct and unique core gameplay systems.
