I agree that "hero" is misused a lot. Everyone knows that the correct term is "sub" or "grinder."
I'm a "hero member" of this forum, and I haven't saved any lives that I know of. I don't think the H word has been cheapened, necessarily, as much as it's just interpreted differently. To some people a hero is someone who saves lives (e.g. doctor). To others, it's someone who risks his own life to save others (firefighter, soldier in war zone). To others still, it's this definition from the dictionary: "a person ... who is admired or idealized for courage, outstanding achievements or noble qualities." Helen Keller is one of my heroes, and I don't recall reading about her running into any burning buildings or falling on any grenades.
One word I think definitely *has* been cheapened/corrupted is "diva." It means a (figuratively speaking) larger-than-life female singer -- think Maria Callas or Diana Ross. It doesn't mean just any famous female singer. (Sorry, Britney.) And it definitely doesn't mean spoiled, obnoxious female. (Sorry, all you "Toddlers & Tiaras" moms who describe your daughters' tantrums as "diva moments.")
And I can definitely live without hearing any other syllables amputated and replaced with S: "totes," "adorbs," "whatevs."