This is a giant robot show but not the brooding-teenager/psychological-symbolism kind of giant robot show. This is the kind that focuses more on heroics than teen angst -- the "I want to save the world because it's the right thing to do and because I want to protect people" kind of show. And it throws in an extremely generous portion of in-your-face fan service to boot.
You won't find any hard science fiction here. The character, costume, and robots are designed to be flamboyant and dramatic instead of practical and functional. The show aims to please its audience with a combination of fond nastalgia for shows like Voltron, but also by reveling in its own low-brow excesses.
The animation focuses on two visual themes: giant robots and giant breasts; and the staff seemed to concentrate equally on animating both. A show that relies on visual energy like this one can break-down quick with the animation quality. But luckily, the quality is relatively consistent throughout.
Your enjoyment of the show will probably depend how you interpret the fan service. If you think of it as satire then the joke will probably get old quick. But personally I interpreted it (rightly or wrongly) as the animators being intentionally obnoxious and just generally having fun with the animation -- like a running gag where they are testing how far they can take it. And for some reason I found that hilarious.
The story is fast-paced and high-energy at the beginning but slows down at about the midway point. That's when the characters get a little more serious as they try to get their lives and relationships in order. It concentrates a lot around the love triangle between Goh, Anna, and Mira. Goh is married to Anna, but only after he thought his previous love, Mira, was dead. But after Mira comes back to life it causes all kinds of awkward moments. I never really liked this story thread, mainly because I really didn't think any of them should be together -- Mira was like the pining mistress, and Anna was just too young for Goh (17 vs 30). It's hard to take much of this too seriously though, since the T&A is in plentiful supply throughout.
The last few episodes pick back up the pace and ends the series exactly how a show like this should end: with an over-the-top battle sequence, explosive climax, and satisfying resolution that wraps up most of the plot points while giving closure to all of the characters.
So in the end, I'm not sure I could call this a great series, but neither is it a bad one. Ultimately, you're not going to get any deep thematic value out of watching Godannar. But it has plenty of energy and can be fun to watch, and sometimes that's all I need.