Repeated Main Themes in Super Sentai

Well there are Super Sentai series that carry the same main theme, however can vary in some ways.  Here are some of them:

Changeman (1987) and Ohranger (1997)- Both are focused on the themes of young soldiers facing against an invading force and coping up with life in the military.  Both were militarily themed although Changeman was all about organic aliens, the Ohrangers faced against machine beings like the Biomen did.

Maskman (1988) and Jetman (1991)- Both had the theme of red rangers with missing lovers.  Well, it's all about duty over love life kind of stuff.  They both had their romances although Jetman took it to a greater level.

Turboranger (1989) and Carranger (1996)- Carranger basically follows Turboranger's car motif, the adaptation was called Turbo probably in tribute to Turboranger and that while there are differences, the mecha in Carranger look like a modern version of the mecha of Turboranger, both using Car Magic powers.  However Carranger was a lighthearted show in contrast to Turboranger which was pretty serious in nature.  What's pretty interesting is that in Gokaiger, the episode where Kyousuke Jinnai appeared also featured the Turboranger powers.

Fiveman (1990), Gogo V (1999) and Magiranger (2006)- Gogo V for me was basically somewhat was an upgrade of Fiveman in terms of maturity, plot, equipment, villains and even script writing.  Fiveman was pretty kiddie compared to Gogo V being more appealing to the older audience. Magiranger was more appealing to children than Fiveman but it had better writing though.  All three focused on the family theme executed in different ways.  

Zyuranger (1992) and Abaranger (2003)- When I first saw Abaranger's concept, it was basically following the dinosaur theme of Zyuranger but applied in a much different way.  So far, Abaranger turns out to have better, more mature writing than Zyuranger.  What's even more interesting is that in both series, the Power Rangers adaptations both have Tommy in them.  Abaranger obviously was inspired by Zyuranger but it turns out to be much fresher.

Kakuranger (1994) and Hurricanger (2002)- Both shows had ninjas as the main theme however the execution was pretty different.  Compared to Kakuranger, Hurricanger relied less on mystic arts and more on the scientific side, in fact IMO Hurricanger was closer to paying tribute to Liveman than to Hurricanger though.

Gaoranger (2001) and Gekiranger (2007)- The main theme was on well. wild animals except Gekiranger was more martial arts based.  It's hard to think what Gekiranger's main theme was as it seemed to fuse Dairanger with Gaoranger in some way LOL.  Compared to Gaoranger, Gekiranger was a more mature, not so standard Sentai team series with a really awesome script and story.