That's a pretty good question actually... which pedal reverb was the first to get me interested in big ambient spacey shit.... I actually don't remember, but it was definitely pre Strymon. Particle Reverb on the Line6 M-series definitely needs a shout out, but there were plenty more too.
I used to use the Digitech Hardwire reverb and delay as my main ambient effects, but I actually found the reverb a bit too limiting. I sold it and that was when I got sucked into the Strymon world I think. Going back a long time so can't really remember. I bought another one of those RV-7's a few years back, and it was really good and nostalgic to have the pedal I recorded our 2nd album with, but in the end I came back around to feeling like it was too subtle and not flexible enough.
The Boss RV-5 was the 2nd pedal I ever bought. The first was an Ernie Ball Vol Pedal!!!