I put 1995 Passengers, but that's not completely accurate. Actually, HMTMKMKM in the summer of 95 was what first really got me into U2. Plus VH1 showed 10 U2 videos in a row once that summer, and that got me interested. My Dad already had Rattle and Hum, my uncle had the unedited tape of UABRS, and a few days later I had my mom buy me Joshua Tree and Achtung Baby (I was only 13 at the time so she had to buy it for me), and after that, I was hooked.
The wait for Pop wasn't too bad, because in the 2 years between 95 and 97, I had time to slowly buy all of U2's albums and discover them. I remember October was the last one I bought. But then, after Popmart, it was 3 very long years until ATYCLB.