I was 12 years old and I took my allowance to the corner store to buy some candy, and while I was there I thumbed through some comics on a spin-rack. One of them was Amazing Spider-man #238, which introduced the mystery of the Hobgoblin. I was vaguely aware of the Green Goblin and the death of Gwen Stacy from comics my parents bought for my older brother when I was five or six, but Marvel didn't really grab me then. But the feeling of getting in on the ground floor of a cool new villain (who seemed like he could be the ultimate SM villain) was too tempting. So I started picking up PPTSSM, where I was amazed to see that Dr. Octopus and the Owl were in the middle of a war, with Spider-man and the Black Cat caught in the middle (and the Black Cat was gravely injured). I started picking up back issues to find out who the Black Cat was.
Eventually Spider-man was considering joining the Avengers. I bought a few Avengers issues, and was entranced by Vision and the Scarlet Witch's mini. Avengers crossed over with FF (the Annihilus barrier issues), and I was hooked on both. I found the great two-part Thanos story from MTU and M2in1. And I found Avengers Annual #10, which hooked me on Rogue. When she joined the X-Men I started picking up that title, and collected it all the way back to Giant Size X-Men #1. I was absolutely blown away by the quality of the writing and the inter-connectivity of this amazing shared universe.
Somewhere around 1992 I gave up on Marvel. When Vertigo's Sandman ended I gave up on comics altogether - money was tight, I had moved into my own place, and it wasn't a priority. Then along came JLA-Avengers, and I was hooked again.
That was a great time to read Marvel. So many great titles. Spider-Man, in particular, was awesome, with the storylines you mentioned and the earliest issues being reprinted in Marvel Tales.