 If you liked
Shin Getter Robo tai Neo Getter Robo
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 ...then you might like
Tengen Toppa Gurren Lagann
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Both feature the struggle of humans against non-humans, a mecha with god-like powers, and an emphasis on drills as weapons, though with Tengen Toppa the drill is symbolism representing humanity moving past obstacles and climbing higher - or a sexual metaphor in some cases.
Both anime also feature hotblooded heroes and combine humor with drama. Although, Tengen Toppa features a set of romantic subplots as well.
I view Gurren Lagann as a homage to the over the top mecha like the Getter robo series. I reccomend this OVA either if ur a Getter newbie or Getter Veteran