I haven't seen it, but judging from the trailer and Wikipedia entry, The Motorcycle Diaries portrays Guevara positively.
It isn't a Hollywood movie (the production companies are British and Argentine), but it was distributed by a division of Universal Studios.
It's about Guevara as a young man, before he became a revolutionary.
I wanted to bring attention to two posts from Razib Khan's Discover magazine gene expression blog (some of you may have been readers of the still active original gnxp) on the polemic surrounding Pinker's The Better Angels of Our Nature.
Relative Angels and absolute Demons (and the related But peace does reign! )
I generally agree with some of his arguments, but found this quote especially as summing up some of my own sentiments: