I watched God Sigma after having completed the original Robot Romance Trilogy and Beast King Go Lion but it doesn't compare to either of them. For starters the heroes are unbelievably bland here with the most interesting characters being Minako Martino and the villains Terral, Gila and Leitz. The conflict doesn't have the initial impact as the Robot Romance Trilogy or GoLion and this is because Terral, Gila and Leitz are meant to be sympathetic villains with Terral eventually joining the good guys. While this makes Terral a much more interesting character it makes the conflict early on feel somewhat toothless. Once the new villainsare introduced around episode 30 the series becomes far more interesting though this is only on the villain's side with the heroes still feeling unremarkable. I felt this is one area where God Sigma did a little better than its predecessors as it tries to kill off its old villains for new ones similar to Combattler V but it does so in a way that they aren't just killed and forgotten, Terral lives and harbors resentment towards them. The animation hurts the show as most of it was outsourced to Taiwan and Korea. The director said the Taiwanese animators hated working on it and used to draw straws in the form of chopsticks to determine who would have to animate the more complicated scenes. He mentions an episode that was made hastily due to a fire destroying many animation cells and I suspect this was episode 3 which hands down has the worst animation in the entire series (missing in-betweens, wrong characters mouths moving while another character is talking, cells placed on incorrect layers, ect). Overall I only recommend God Sigma if you feel compelled to watch it, I did it for the bragging rights of being able to say I've seen every shows in the Saburo Yatsude/Popy production line that followed Nagahama's Robot Romance trilogy. If You want a better combiner mech anime I recommend Combattler V or Voltes V and if you want a better time travel mecha story I recommend Baldios.