This is actually really easy to answer because when I first read this the only thing I could think was the Mass Effect trilogy.
There are many games close to my heart (Age of Empires was my first ever video game, and Age of Empires II: Age of Kings remains my favorite RTS, while Legend of Legaia was the first ever RPG I played and fuck if I don’t miss and love that game), but Mass Effect really struck a chord within me.
Grab a chair and a drink, folks, DT is going to get wordy.
I didn’t actually play the first game until well after I’d played the second; I did, however, watch my brother while he played, so I was well-acquainted with the story when I got my hands on ME2. I was pretty much a backseat gamer; I often urged my brother to make certain decisions or dialogue choices (sometimes he listened to me, sometimes he didn’t), and I’d often fire up his XBox to read through the Codex on my own time. (I couldn’t aim worth a damn with the controller, so I never started my own game.)
I was fascinated by the story BioWare had crafted, by the alien cultures, by the crew you gathered, by how you could shape Shepard’s background and personality and make your Shepard a truly unique protagonist.
I became completely attached to my own FemShep when I began playing ME2 (I received a free copy of it for preordering DA2 way back when), and while I used an original ME save import from the masseffectsaves.com site, I quickly purchased my own copy of ME through Steam so I could make my Shepard’s story exactly the way I envisioned it.
I love my Shepard. I love all the aliens of the ME galaxy (with a special shout-out to the dextro species, muahahaha). I love the crew of the Normandy. I love to hate Saren and the Collectors and the Reapers. I love how these games have evoked such strong emotions in me (crying over the decision on who to leave behind on Virmire (my brother was also shaken by that and agonized over it his first playthrough), cheering when Shepard walked out of the rubble of the Council chambers, crying again over the destruction of the Normandy, fierce pride when I successfully got my entire crew through the suicide mission, the fucking emotional roller coaster that is ME3 with all its triumphant highs and truly heartbreaking lows).
Mass Effect isn’t perfect; for instance, I’m still ambivalent about the ME3 ending, but that’s what fanfiction and headcanons are for, and it’s a topic that’s been argued to death by more articulate fans than I. But I love the series anyway, because BioWare created a story and characters that made me care about and agonize over them, because BioWare gave me the options to shape how I wanted my hero to think and act, because BioWare infused so much life and detail into this universe that I couldn’t not love it.
The Mass Effect games are my perfect games.