Gundam is a must watch, obviously. Try the 0079 movie to save time trying to get into UC (Personally I've never even finished watching the original series).

Star Driver has awesome fight scenes and a story that feels surreal, kinda like Utena.

I watched New Getter Robo many years ago. I tried reading the manga but the beginning was much more boring compared to New Getter's awesome first episode. Haven't read past that.

Top wo Nerae is so awesome, the story and the action scene is top notch.

Macross is famous for the missile circus, but the focus of the story isn't the mech, so while I do enjoy it, I'll scratch it from the mecha anime recommendation.

For a bit of change to those classic super robo lovers, try Robot Girls Z