This is not one of those cases. In a way I must say this series actually have a much better origin than the original. I love the fact that Tony is a minor and two years away from becoming Mr. Stark (owner of Stark Industries) because that opens up a lot of story to tell. Also this series is not at all childish as I expected. The dialogue is really well written and all the voices, except Peppers, is really great. Also it's a very serialized series which makes it all the more enjoyable when you watch all episodes. On the other hand it makes it harder to get into if you're missing episodes.
Actually the only really bad thing with this series is that damn Pepper Potts. She's so damn whimsy and talk so much smack with that annoying voice. I just want her to die but that would probably ruin the origin story a little to much =). It's not something that ruins the show but for me it keeps it from being perfect. It's a strange choice to make Pepper so childish and annoying when everybody else acts so mature.
Take it from someone who really dislikes it when they screw up origin stories.. This series is great! It doesn't screw up the origin, it makes a new one. One that is superior to the original. The animation seems a little bit off in the first episode but as the series progresses it gets much better. The big nemesis for Tony, The Mandarin, is made really well, as are all the other enemies as well. The only thing this series is lacking right now is some solid crossovers from other famous marvel characters but I'm sure that'll come.. Also WAR MACHINE is soooo much cooler in this series than in the live action movie! The pilot is really bad compared to the rest of the series so give it a shot and I'll think you'll be pleasantly surprised to find a mature animated show about one of the cooler Marvel characters. Even though he's depicted as a teenager.