Unlike many people, I didn't watch any anime at all in my (younger) childhood. Although I was somewhat aware what anime was for a while, I never heard anyone talk about it until a few years ago when some people I knew spent somewhere around a month or so talking about little else besides Attack on Titan. At the time, I really didn't care. I wasn't interested and and I thought I was never gonna watch it anyways, but it was nigh impossible to forget the name. A few years later, late spring of 2015 to be specific, my dad got a new job and I learned that I was moving away from what had been my home for the past 11 years. In late-summer of the same year, we had finished moving in and I really missed all my friends. Then one day when I was particularly sad and lonely, I thought, "Well, I think I'll try watching Attack on Titan, it's not as though I have much else to do". So I started watching. And I watched all of season 1 in about three days. After that, I thought I may as well try Sword Art Online (because those guys I mentioned earlier talked about it a bit). So I started watching SAO and I even stayed up all night one night to watch it.
So although I would definitely consider Attack on Titan to be my starter anime, Sword Art Online is responsible for making me learn a few things about myself. SAO taught me I could be emotional over something fictional and there are fictional characters in whom I can find no redeeming qualities (Sugou). AoT is what got me into anime and SAO is what made me stay.