I genuinely can't think of anything that entranced me as much as the art style, character and mech designs and world of G-Reco. I mean I adore Kenichi Yoshida, and I'm as big a Eureka Seven fan as I am an anything fan, but obviously that was over a decade ago, and even that had a lot of sparseness and muted backgrounds at times. The only mech series that's as lush as G-Reco is the Rebuild series, and that's a god damn massive movie franchise.
Side note, the moment in the ED when Bellri walks arm in arm with Cahil and Dellensen? The two men who's deaths he regretted so much? One of whom clearly felt paternal towards Bell? Destroys me every time I see it