I would say Mask and Dino Riders. However I have no place to own armies of action figures with gigantic vehicles/dinosaurs as a gimmick. Oh, and don't do the modern dinosaurs with feathers, do the dinosaurs from my childhood. On the other hand I don't know if I would like the outcome of a reboot with todays toy economics in mind. Thin plastic and waffle molding on Mask Vehicles, no thanks! Thinking more about Mask Vehicles I would love to see an approach with transforming vehicles that don't rely on spring mechanisms. I would prefer a Transformers based approach where you have to transform them by hand but have a more intricate transformation as a result.
Top of my wants would be: Micronauts....cmon Hasbro, you've been teasing them (and us) for YEARS now... Exo Squad...it was ahead of its time then, I'd love to see what they could do now! Kenner Aliens...not the Neca, looks nice but will snap like a twig if you look at it sideways....much less attempt to touch it... fragile, poor QC 'figures' Neca likes to crank out. I want ones that can be played with by kids with all the gimmicks of the 90s line. Zoids...i loved building them and with so many different models they could keep cranking them out.
Pretty much any of the classic stuff from Mego... save perhaps the Love Boat line. But an emphasis on Micronauts.
Thundercats - why someone can't get this done properly and at the very least give us the Mumm-Ra, the original six cats and the original three mutants is beyond me. Right now Mezco seems like it's the only hope for a 6" Thundercats line done properly as they stated they could do Thundercats in their One:12 line. GI Joe - a 6" Premium collectors line please. I'd take the main characters. Don't necessarily need troop builders here. Why, in the era of toy collecting when 6" is the main attraction, I can't imagine why Hasbro hasn't taken a crack at this either at retail or through HTS. The fact that custom 6" figures sell on eBay for upwards of $200 to $300 each should show Hasbro that a market exists for good quality $20 retail figures. Ninja Turtles - probably a pipe dream with Playmates cock blocking Neca even though they don't want to continue doing a collector based line themselves... but a good quality collector's line that doesn't cost me an arm and a leg at SDCC every year and isn't cancelled by Playmates because they want to put out three or four different versions of the Turtles back to back and then claim that the figures don't sell. Visionaries - Loved the show and comics as a kid and would love to see a 6" reboot of this line. Inhumanoids - Same as above... in fact it's really amazing that Hasbro has so many properties they've just let sit since the 80's... Silverhawks - Love this show as a kid. It was right up there with Thundercats and He-Man for me, but I never could find the toys at retail back then. Dinosaucers - Loved this show growing up, but it seems the toyline was canned before it ever started from what I've looked up. Mask - But without the spring loaded gimmicks. Make them more like Transformers where you have to manually convert them to their battle modes. Dino-Riders - Why hasn't this come back? What child wouldn't want a T-Rex decked out in laser guns and rocket launchers? Robotix - Never had the toys as a kid, but the TV special seared these guys into my brains. I'd love to see them make even a small comeback. Centurions - Again, why this hasn't made a comeback is beyond me. Especially as popular as Iron Man is since the MCU and these guys are all basically specialized Iron Men. Captain Power - Had a few of these and really enjoyed them.
For maximum playability and variety: Centurions Starriors For playability and interesting gimmicks: MASK For interesting concept and story: Inhumanoids Starriors (yes, I know I did this one twice) Bravestarr IMO the best line to bring back is Starriors. Strictly as toys, the ability to mix and match parts to customize figures makes for an insane amount of playability and lends itself to community activity in showing off one's build. From a financial standpoint, buyers become incentivised to purchase duplicates in order to have more parts to use. In addition, the lore of the setting is extremely compelling. Not for nothing, but the two factions are very reminiscent to me of the Vorlons and Shadows from Babylon 5. There's enough maturity to appeal to legacy collectors with enough simplicity to draw in a new generation of young fans. If this isn't brought back officially, it should be a kickstarter.
