I think from today's standpoint, Kuuga and Agito do invoke a certain nostalgia, as the story was quite a bit more simpler and more reminiscent of the Showa Riders. But when it first came out, Kuuga was considered a radical departure from the styles of the Showa riders. Kuuga didn't call out his attacks, he had multiple forms, the police were involved, he never fought an evil organization, and he wasn't a cyborg. The story was realistic, and in the sense that the people weren't all cartoony like today's characters.
Again, this is my opinion. You have to see Kuuga for yourself to see if its that good or not.