"Eiji"

Both themes are boxing. But the way of being a boxer was different. Both VERY funny in their own way. In my opinion both are very epic and exciting. Their personalities are VERY different or rather they are complete opposites.  

Both are about boxing, both Eiji and Joe, are not interested in boxing at the beginning and the old man convincing them to try it, cos both have really good talent for it. Ashita no Joe is a dark, realistic show about boxing. eiji has a really good atmosphere, aesthetic vibe, promising plot but sadly, I can't say much more about eiji, because there is only one movie, but as a Joe fan, I can say that this had a potential and I enjoyed this movie and wish there was more to watch.  

Similar audiovisual style and "rebel youth" vibes. 

Both are fighting sports anime. Neither really gets into things that usually make sports anime dead boring.  

While Slow Step includes some romance elements, both are old sports anime. Also boxing. 

Sex crazed youths trying to find their next ambition. The '90s sure was a single-minded time.