Well, it depends on which side of the mech genre you`re talking about. Gundam was the first to portray the mech as just
another machine of war, something for good or evil dependent on the pilot, and with limitations.
Evangelion moved the mech into a different realm, something breathing and alive and with far more purpose behind it than
the simple human pilot knew.
And Mazinger...it was kind of the daddy of the current ones, aint it? I know Gigantor was around, but Mazinger was, to
my knowledge, the first one piloted by a person instead of automated or remote controlled. Not to mention its a classic
Giant Robot anime, a big heroic asskicking robot!
So I have to go with gundam, but those three series each have their own landmarks made. Id comment on Macross, but Ive
only seen Robotech and I know thats not the real macross ;)