Final Fantasy X - My favorite game of all time starring my favorite character of all time (any medium). Also the reason I avoid localizations and go out of my way to play/watch/listen to media in the original language whenever possible. Hell, you could say I owe my career to this game.
Super Smash Bros. Melee - Probably the most hours I've spent in a single video game? Either this or StarCraft if I had to guess. Also the first place I really started frequenting on GameFAQs (and the internet in general) was the Melee boards back in early 2002, which eventually led me to Board 8 where I've been trapped for almost 20 years. This is also the only fighting game I played at a semi-competitive level and got me into the tournament scene for awhile. I was into Target Test and Home-Run Contest for a long time as well. Oh yeah, on top of all that, it got me into Fire Emblem too, which is another one of my all-time favorite series.
Pokemon Yellow - This was the first game I can remember being absolutely hooked on. As a kid I rarely finished games and just moved on to something else half-way through (okay fine I still do this) but I was absolutely immersed in this one. I remember playing it at recess and being so locked in I missed the bell. To this day I still play every mainline Pokemon release and remain a big fan of the series, and while Gen 1 sits at the bottom of my rankings, I can't deny the influence.
Persona 5 - Not really influential or anything, just an amazing game. The only game to challenge FFX for the top spot, and there are days where I would put it number one. The one thing I can say for it in terms of legacy is it got me to play Persona 3 and 4, which are also great games I enjoyed a lot.
HM: Hollow Knight - Got me into Metroidvanias, now one of my favorite genres, and killed my anti-Indie bias. Also just a great game
MZero, to the extreme
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