Because I read the books a few years back (I needed something to nap to then, too), and my impression was that, at the very least, Isildur deserved the benefit of the doubt for having been seriously contemplative of the question of what to do with the Ring after It came to him. He was deeply conflicted about choice - and the subtext was clearly that his deliberateness was exploited by the Ring, that's how smart that fucking Ring was. Maybe the Ring won't bring you the paper, but it will certainly put your dog to shame.
Unfortunately, the way the movie makes it sound, Isildur was this weak-willed, incompetent hack with a sniveling expression, and not a single line of dialogue with which to redeem himself. Personally, I would have made Isildur's part a musical part, and made the movie 20 minutes longer to squeeze his story in there.
Take note, lord of the rings: the fellowship of the ring, the movie: there's a reason I capitalize The Ring, and not you anymore. I am not to be trifled with. Just ask juggs rinehart the blah*. You know what time it is?
(* the artist formerly known as Judge Reinhold)