In the past decade or so, Hollywood has learned to -- sporadically -- make movies which capture what's good about Marvel superhero comics. The first two Spiderman and the first two X-Men films are examples of this (And in both cases the third movie in those series were distinct disappointments). And so is Iron Man.
Now, nobody (I suspect) would pretend that Marvel superhero comics (which -- unlike the other major superhero publisher DC, which produces a bunch of other things too -- is pretty much synonymous with Marvel comics, period) are High Art. I hope I don't need to convince anybody in this day and age that a lot of comics are (and many more aspire to be); it's even true that some superhero comics are High Art. But that -- a few oddities aside, perhaps -- isn't what Marvel is trying to do. Marvel makes comics that are the comics equivalent of summer popcorn movies: fun, funny, exciting, nothing to think too hard about.
And that's what they've done well, recently. They've made superhero movies that have a sense of humor, that are exciting and fun and enjoyable if that's what you're looking for. And Iron Man is one of those. It's funny (a key component in such movies); it doesn't try to cram too much in (ditto); the lead actors turn in good performances. It has good special effects and it's a good action movie:. In short, it's very enjoyable; I liked it a lot. Excellent light entertainment. -- Don't think about it too hard: you'll break it. Just put it down gently. There. Like that. See? Lots of fun.
(There's more to say about this whole 'making a good Marvel comic movie': what works and what doesn't, what they include and what they omit, a precise description of the spirit they capture. Perhaps I'll get into it later, but for now: Iron Man does what it tries to do well; if that's what you want, then by all means, see it.)
Oh, and if you go, stay through the end credits -- Iron Man is one of those films that tucks a scene in there at the end.
Speaking of Iron Man, you can watch a funny Iron Man/Batman youtube here.