I don't know why anyone should be ashamed to go see the G.I. Joe movie. I've already read the novelization to the movie, and if it's anywhere near that, it's going to be a good popcorn movie. Even though I grew up with these characters, I'm not a purist and I like the different spins they've taken with them. I could care less if G.I. Joe was an American team in comics and cartoons, because it works extremely well as an international team within the context of the movie (once again, going by the novelization).
But some people really want to see the movie fail for some reason, but I think the movie will strike the right balance of action, drama, dry humor, and the occasional over-the-top military hardware that G.I. Joe has always been known for.
I'm already hoping for a sequel...