I guess I basically like the stories and animation of these. They were a short series, maybe about 6 episodes. There is a basic compilation into a movie of both series. But I like the full series. You can watch these over youtube, which I just found out this week. Ageing part, I still like watching them. Robot Carnival, which is a movie, is another favorite. There are those that I watched years ago, I'm talking like 18 years, on the syfy channel, back when I had cable, such a long time ago and technology was so different, that have aged like you are referring to. There is one Roujin Z which I still like from that time period. I think the weird oddity of Robot Carnival and Roujin Z is what still makes those two enjoyable for me to watch.
There is so much good anime now as it has gotten better over the years.