Super Sentai started as Secret Task Force Goranger. Sentai, since Zyuranger, is adapted to America known as Power Rangers. It has the same concept but different in it's own way. Each series from the past 15 odd years each sentai ends up with 5-6 rangers. Usually it's 6 but recently Detective Task Force Dekaranger had 10, yes 10!!
It is hard to review Super Sentai because each series is different, and I can't review all 29 existing series because I haven't seen them all. I suggest watching each series and finding out for yourself. I can attempt to make a summary for all I know
Goranger - Goverment project
Zyuranger - they get their powers from the dinosaurs. They fight the evil witch Bandora and the evil her assistant PuriPuri makes.
Dairanger - 5 stars from above. They fight the gorma clan in order to stop it from taking over the planet. They later get a kid ranger, kibaranger.
Kakuranger - 5 Ninjas that cut and eliminate evil! Kakuranger revealed! What is interesting about this one is Ninjablack is American who barely speaks Japanese.
Ohranger - Dealing with Egypt and pyrimids I think
Carranger - Cars
Megaranger - They are space rangers
Timeranger - 4 cadets from the year 3000 are stuck in 2000 trying to stop a villian who escaped from the past. Ironically, they find a red ranger in our time to fight with them who is in relation to an evil man in the future, whom they, at first, think he IS that evil man.
Gaoranger - 5 chosen soldiers of the animal spirits band together to stop the evil orgu. When the last, Gaored appears, he wants to change things with the team, including a name basis. Gaoyellow makes everyone call each other Gao instead of their names. He believes they loose their identity.
Hurricanger - Ninja's again. They start out with 3 then add 2, then in the end, Shurikenger, has an interesting story, I suggest looking into it.
Abaranger - Dinosaurs again! They must use their changers to call upon dinosaur powers to fight against evil.
Dekaranger - Detectives. No real solid story. They investigate different crimes and make arrests. That is pretty much it. However, what I find disturbing is they kill their enemies, even if they haven't committing bad crimes. In SPD, dekaranger's American version, they are arrested.
Magiranger - 5 brothers and sisters must join forces after evil kills their mother. The evil forces of hell (yes hell) are attacking to open the door so all the monsters will be unleashed. The magiranger's mother is also a ranger.
Well overall i'd say it's a fun series...the drama can be worked on, acting should be amped. I am sure people will agree with me. Those who don't are usually giving out illegal subbed copies of it ;)