I was taken in by the Divine Dungeon and Slime Dungeon at about the same time. So much so that I get the two confused.
Was either The Land or Alterworld by Rus, then I found Awaken Online and was well and truely hooked after those three. Wow totally forgot about Quag Keep, got both the first and the second in that series. Thanks for the reminder.
My first was Sufficiently Advanced Magic when it first came out... I love that Clarke quote, so the title piqued my interest... From there it was Divine Dungeon, followed by D. Rus' Alterworld...
When I was a kid, I watched TRON and the Dungeons & Dragons cartoon ('82 and '83, respectively). Reading-wise, it would have to be Larry Niven's Dream Park, which I read back in the late 80s or early 90s. I haven't read any current LitRPG, save for Ready Player One, NPCs, and Off to Be the Wizard, and I guess people argue whether those three even completely fit the genre.
Also, I think I stumbled upon the first book of Adventures on Terra and that led me to...the Land and then Delvers LLC.
Sadly I'd have to go back and reread my first book to figure it out. I *think* it was Alterworld, but I could be wrong. I know the author is Russian. I know I loved the first few books. However at some point I felt the author was being rather misogynistic, which was odd since the MC's 'bodyguards' were dark elves women! There was also a lot of Stalin popping up. I've nothing against strong leaders, and I realize that as an American I've already been raised with a bias against Russia of old. Stalin was brutal though. Ruthless even. Anyway. Maybe I should give them a try again.
I think it would be Guardians of the Flame for me, though I only had the first few books. I really did enjoy Piers Anthony's Killobyte, but that wasn't LitRPG so much as gamelit. More recently I think Alterworld: Play to Live drew me in followed by The Bathrobe Knight.
I wrote the book that got me into litRPG. Kinda. I keep mentioning it: 10 years ago, I came up with that concept...
I read Killobyte by Piers Anthony in high school and loved it. Then when Ready Player One came out my daughter brought it home and I read that in two days because I was so sucked in. It wasn't until a year or so later that I found Crucible Shard and realized THERE'S A WHOLE GENRE! and I've been reading it ever since. I read so many that I started writing it, too.
For me it was Emerilia that sucked me in, I think. The Land, Life Reset, and Limitless Lands remain my favorites.
My first was Robert Bevan’s Caverns and Creatures books, just brilliant. From there I sought out more of the same and went onto Drew Hayes and then the Chaos seeds.
