The former because it’s an experience unlike anything else I’ve ever had in gaming, and the story and meaning stays with you for years afterwards (possibly forever, but it’s too soon to tell.
The latter because the very idea of being able to really explore Azeroth after years of playing the Warcraft games was the most exciting thing ever, and the moment I first exited the orc starting area and looked at the map and saw how big the world was will never leave me.
Books: The Hobbit. Read it when I was 4, with a not insignificant amount of help from my dad. It was fun, it was thrilling, it was scary, and it kicked off a lifelong love of reading. For an adult it’s a very short read that will probably only take a couple days, which is also a big plus.
Honorary mention to Thud! by Terry Pratchett. Really the Discworld series as a whole, but that one particular book is the absolute perfect blend of comedy, social commentary and downright horror. Again, very much stays with you afterwards.