Generator Gawl is an outstanding series purely from a plot perspective, and the perfect show to introduce someone to Anime. To be honest it feels a little rushed at times, as if maybe with about 3 or 4 episodes the story could really have been fleshed out, getting that fifth star. As it stands it's still an excellent series. Initially the series seems a bit derivative, mecha, mutants, fighting, but it quickly becomes apparent that "Generator Gawl" is far, far more.
I have to say what really makes this series for me is the story, and the characters. the designs are solid, but nothing spectacular. The animation, again, it's solid, but there are plenty of anime series out there with higher quality animation. Plotwise though, few series compare in terms of twists you just don't see, and characters you really feel for. Koji, Rho, and Gawl give up everything for their mission, and as the series unfolds they sacrifice even more for a goal that seems increasingly hopeless. It's a fantastic story, told without frills, or platitudes. And i really can't say anymore without giving away the story, and I don't want to do that!
You HAVE to watch this series!