>>23470207
G Gundam is my least favorite, it's a bit too long and kind of not on the same level as the others.
It's hard to rank the others, but I probably like Shin Mazinger the best (because I like Mazinger) and it's so grandiose and theatrical
Then probably Tetsujin (2004) which is just great, it's quite serious in comparison to what you might expect
giant robo is some of the best ova animation you will ever see but it's somewhat uneven otherwise, very much worth watching for pretty much any anime fan not just mecha. quite a bit of wuxia type stuff too