For MMPR S1, the setting was completely different from Zyuranger, making it quite original. Instead of ancient warriors, it's about high school teenagers with attitude. However, when it came to the major plot arcs, most people would agree that the plots were watered down versions of Zyuranger's. Such as the Green Candle arc (where Tommy lives and Burai dies tragically). Regardless, the characters were still a fun bunch and was another bit of originality to Power Rangers, despite them being stereotypical.
For MMPR S2, the show completely went in it's own direction. Actually, it was more like after episode 40 (Doomsday) when the show started using the exclusive Zyu2 footage. Instead of using any elements from Dairanger other than Kibaranger's suit and the mecha, MMPR S2 was completely original. Plus, seeing how American shows work, MMPR S2 had to be a direct continuation of the previous season, continuing the story.
MMPR S3 continued being as original as MMPR S2 did. Using Kakuranger's mecha footage and eventually the actual Warrior suits as well.
Zeo used both the Ohranger suits, villains, and the mecha. But like MMPR S1 before, it was still quite different. Instead of the military settings, Zeo continued to use the high school teenagers with attitude. And Like MMPR S2 and S3 before it, Zeo continued the ongoing story with the same characters. So this greatly showed a difference from Sentai, where Sentai's stories ends every year. For Zeo, the season starts off after three whole seasons of stories had already been told. It helped even more when Jason, back from MMPR S2, came back to become the Gold Ranger (KingRanger's suit). In terms of plots, unlike MMPR S1, Zeo does not copy most of Ohranger's story.
Like Zeo before, Turbo used both the Carranger suits and the mecha. This is what Power Rangers would be doing every season now. The villains were mostly an original bunch (especially Divatox). Unlike Carranger, which was a self parody of Sentai, Turbo chose to be serious instead, making it more original, and completely changing the plots for the episodes. Whether for better or for worse, that's up to you to decide. Turbo continued the story from Zeo, using the same cast again.
While the previous five seasons starred teenagers with attitude, instead of ancient warriors, military officers, or automobile mechanics, the team still utilized the same motif from their sentai counterparts. Power Rangers in Space was the first season to completely use it's own motif. Instead of Megaranger's hi-tech digital motif, it used space travel instead. This season was the final season to use the same cast from the previous season. This was also the first season not to be written by Doug Sloan. Instead, Judd Lynn would write it, changing the ways the franchise would be handled. In terms of plot, In Space had originality, like the whole Andros and Karone story. This season did also stay true to some of Megaranger's plots. Such as the Psycho Rangers arc. Whether this was for better or for worse is up to you.
Like In Space before, Lost Galaxy did not use Gingaman's mystical forest and nature motifs. Instead, it used the space travel motif again, taking place on the space colony, Terra Venture. What makes Lost Galaxy original, is that it's semi-connected to In Space. Elements like Bulk, Alpha 6, the Megaship, the Psycho Rangers, and Karone all return in this season. Starting this season, the cast of characters would be changed every year, just like sentai. Despite now copying one of Sentai's elements, the Power Ranger's casts are still different from the Sentai characters. Though at times, this isn't always the case. For Lost Galaxy, the cast was very different from Gingaman's. Leo, Mike, and Maya all have similarities to their Gingaman counterparts, but are still very different in their own right. In terms of plot, Lost Galaxy does some original things like the journey to find a new planet, Trakeena's relationship with Scorpius, her relationship with Villamax, Deviot's treachery, Kendrix's death, and Karone replacing her. Lost Galaxy also copied a lot of Gingaman's plots. Like Mike's "death," the Lights of Orion, and the Magna Defender. Whether this was for better or for worse is up to you.
Lightspeed Rescue went back to using the Sentai villains and using GoGoFive's rescue motif. Lightspeed Rescue never had GoGoFive's family themes going on, so the plots were very different. But in terms of plot for the villains, they were pretty much the exact same as GoGoFive's. Which basically meant that the overall season long story was just about the same as GoGoFive's, but without the family aspects. Another major original plot that Lightspeed Rescue had going was the Titanium Ranger arc. This arc was the only major story arc to involve family. And some pretty good drama too. Because the family themes weren't the focus of the show, the characters weren't all siblings, which drastically made the cast different from the GoGoFive characters. Lightspeed Rescue was also the first season to not have any connection to the previous season, working more like how Sentai works, from now on. Whether this is for better or for worse is up to you.
Time Force also copied Timeranger's villains (except Ransik) and used the time motif. Not only that, but Time Force also used Timeranger's story theme of "Even if you can't change your destiny, you can always change tomorrow." However, instead of using this theme for the whole team like Timeranger, Time Force only used it for Wes, and eventually, Ransik (in the finale). In terms of plot, Jen's story was very similar to Yuuri's. Yuuri loses her family, whereas Jen loses her fiance. In terms of plot, Time Force was very similar to Timeranger. Time Force's originality seem to be in it's characters. Unlike the Timeranger characters who all had to deal with their screwed up lives, the Time Force characters had other things going on for them. Their problems were still somewhat similar to the Timranger characters.