oh, and if you're interested in a more child-oriented transformers-like show, gaogaigar is a fun time as well
and eva as mentioned above is good too, though I'm hesitant to recommend it as a *mecha* anime. since the focus is far endlessly more on the human cast than the evas, and
the evas aren't actually mechas, but artificially created flesh and blood humans. with the outer "mecha" parts just being implanted on as a control mechanism
Gargantia on the Verdurous Planet was pretty good. I also thought Magic Knight Rayearth was really good, if you don't mind that it's also a magical girl anime.
I've only ever watched NGE and Gurren Lagann, but I enjoyed both. As LambdaDelta mentioned, Eva is much more human-oriented and psychological and can be a bit of a downer, but if you're into or ready for that, I'd definitely recommend it. Gurren Lagan is more fun imo, but it has its heartfelt and sadder moments as well and is overall a good watch.
lets introduce some mecha genre anime,Code Geass ,Muv-Luv Alternative: Total Eclipse and now lets talk about them
Code Geass is a series that many people love. While it is an older anime compared to today's standards, there are many things to like about it. It is a mix of many genres: mecha, psychological thriller, a little bit of romance, and action just to name a few. It is an anime with an engaging story, and characters that hopefully will stand the test of time. The characters are all interesting. Never have I seen an anime with a cast of so many anti-heroes before: lots of jerks, losers, obsessed freaks, and extremists, but they manage to make you intrigued with their lives and the happenings around them.
Muv-Luv Alternative: When somebody says the word "mecha", we would immediately think action and robot vs robot flying and fighting each other. Yes, muv-luv did have these elements, but it also included the mindset of the characters in it.
I'll get straight to the point, Muv-Luv Alternative: Total Eclipse was a great anime that was overlooked by a lot of people.