I'd say Gundam, but that's probably a bit unfair, as I've only really seen Gundam Wing and the Unicorn one. I liked Wing at the time, but I was like 17, and even then I hated the whole teenager angle, and how emo Heero was, and he wasn't alone. I enjoyed the adult characters, and the quasi-adult storytelling, but looking back I know I'd cringe at almost every angle of it

And Unicorn had way too many convenient plot mcguffins for me to take serious. I stopped watching after 3 or 4 episodes

I think the only other one I've seen was whatever was on Toonami back in the day. 0080? I think? That one seemed alright, but I rarely caught it. With that being said, I know I've barely scratched the surface of the Gundam world, so I'm sure there's better stuff, and probably stuff I would actually enjoy in there somewhere.

I've yet to dive into Gurren Lagan because I knew someone who wouldn't shut up about it, and it drove me nuts and completely turned me off. So from my perspective it's overrated, but I've yet to actually check it out to verify. But from what I've seen in previews on Netflix, it looks extremely spazzy, so I would honestly wager it would grate on my nerves even if I hadn't already been turned off to it. But who knows. There's a lot of things on my backlog that look way more interesting to me, but I may get around to it someday

But sadly I haven't had the chance to taste test enough giant robots anime to really get a feel for what's out there, let alone to call out a bunch of specific ones for being bad and getting an undeserved good reputation. My opinion is completely biased and trash in this regard and I wholly admit that