An "international" team of Japanese heroes are assembled to fight the alien invaders using the power of the Dinosaurs, and samba dancing. Kyoryuger was a ton of fun and I really enjoyed it. The toy sales were dismal though, and this is believed to be due to the lack of a gimmick like the previous few years had. The series sort of floundered a bit narratively, despite the addition of some really awesome characters.
In the near future a trio of special agents and their android companions have to fight invaders from a digital realm who are stealing precious energy from a struggling civilization. Go-Busters tried to be a lot more experimental and shake things up after the previous season was a love letter to the past. The gimmick was the Ranger Keys, which are still being produced now! It was super popular with fans but less so with the young kids who are the target audience who didn't care about the older series or guest stars. A group of space pirates have come to Earth looking for the ultimate treasure, and find the ability to channel the powers of the previous Sentai heroes. Gokaiger was the 35th anniversary series, a huge epic plot that for the first time really tried to establish a solid continuity and the fact that all of the previous shows existed in one world. The season's gimmick was cards that could be used at a tie-in arcade game IRL, and the arcade machine was made into a character in the show. A group of guardian angels from another realm get stranded on Earth, living with an astronomer and his precocious son. Goseiger in comparison was rather lackluster. The season's gimmick was discs that you could spin. It starts off seeming simple, but there's hidden depths that the series explores as it progresses. Years ago, a samurai and his retainers banished a demon lord, but now the seal is failing and their descendants have been summoned to fight the evil forces one more time.