I don't now how groundbreaking they were at the time, but I feel a big part of it is attributed to being part of the first wave of anime readily available in the West so a lot of people look back on those titles especially fondly. I kinda hopped onto the train late for those titles. I was also watching a lot of titles at the time so things were getting a bit lost. I didn't spend much time to think, discuss or reflect on those shows as I'd just hop onto the next.The thing is, these shows were either groundbreaking or huge genre turning points. Whether it be story, animations, characters, and most importantly, great or excellent dubbing. What's not helping is certain fans that go overboard and hype these shows like they're second coming of Jesus, bring about world peace, or "changed their life forevah!". I still love Cowboy Bebeop, Trigun, and Outlaw Star, and consider them the Holy Trinity of Space Western anime, but even I recognize their flaws. How little they have though, but recognize them none the less. Evangelion can fuck off though. I hate back when I wasted my time with it on adult_swim, and still don't like it, but don't care enough to get bother by it or the fandom.
Meanwhile titles like You're Under Arrest, El Hazard, Rurouni Kenshin or Dual have left a greater impression on me due to them being some of the first titles I watched as I was getting into the hobby. They were what was airing on AXN Asia's anime block, and I guess that's my equivalent of whatever anime was on Adult Swim for other parts of the world. I didn't have AS where I'm from. I was also watching them on a TV schedule as opposed to binging, discussing them with my friends at school and stuff.