Question...as someone who enjoyed Power Rangers until the end of Lost Galaxy and fell from watching it after that point, are Dino Thunder and RPM recommended watches before the new season comes with all of its guest-star goodness?
Sadly, neither season will be represented in Super Megaforce, as the only Disney-era Ranger returning is Casey, the Jungle Fury Red Ranger. Saban really does not like the Disney seasons.
Here's a little pro and con rundown of the Disney seasons:
Ninja Storm:
Pro: Unique concept, different costumes, some decent lampshade hanging, a different and nice Battilizer, anything and everything to do with Cam.
Con: The music is all kinds of bad, the extreme sports seem tacked on, emphasis on comedy over drama, Blake had no personality, most everything having to do with Sensei, Lothor, Lothor, and Lothor. Also, the Zords are pretty meh.
DinoThunder:
Pro: Strong cast, return of Tommy, great White Ranger costume, excellent villains, great theme and music, fun dialog, great team up episodes.
Cons: Ending is pretty meh, the main Ranger suits are bland, Jason David Frank missing for half the season, true introduction of civilian powers, the White Ranger storyline being bumbled near the end, Red Ranger Conner gets a million power ups.
SPD:
Pro: Good premise, decent villains, great mentor, nice suits, fun Zord battles, interesting character dynamics, A Squad.
Cons: Kalishspolions, a lot of background info is missing, the team up episodes sucked, pretty much anything and everything to do with Sam the Omega Ranger.
Mystic Force:
Pro: Good costumes, trying something different, Xander.
Con: Nick steals the show for no reason and is arguably the worst Red Ranger, the story concerns the secondary characters so much the Power Rangers feel like guest stars, doesn't keep the Sentai spells consistent, the horrible theme
Operation Overdrive:
Pro: the "Once a Ranger" 15th Anniversary special, the Ranger suits are nice, "Once a Ranger," the revelation about one of the Rangers, and "Once a Ranger.
Con: Everything else. Plus, the Black Ranger gained the wrath of the fanbase at the last Power Morphicon
Jungle Fury:
Pro: Good-to-great cast, strong characterization, excellent fights, good music
Con: Story is bland, costumes are meh, Fran never morphed
RPM:
Pro: Excellent cast, excellent writing, actually funny, gives explanations to regular PR tropes, a Scottish Ranger, good villains, tragic back stories for everyone
Cons: Some of the fights can be a letdown, the mook soldiers are pathetic, the final fight could have been better
If you don't mind spoilers, Linkara has reviews of all the seasons up to Mystic Force in his History of Power Rangers features.