My preschooler is a big fan of Iron Man: The Armoured Adventures. Having watched a little I quite like it too. Pepper Potts also has a powered armoured suit which, unlike the outfits of most female heroes in the cartoons of my childhood (Voltron,Battle of the Planets... ) isn't pink. I just wish there were more female superheroes on tv. I guess there's the Powerpuff Girls but that's not on free to air at the moment (at least, I don't think so, we only watch ABC Kids).
I also used to enjoy the Amazing Spiderman and the Batman animated series.