Well I went the other way around. And yes, it is not comparable to the manga. They should probably not even be compared.
The film though has its merit - as a film. As a 2 hour piece of fiction. It's fast paced, coherent enough (though it seems some find it confusing - I thought it flowed pretty well), and it has some impressive cinematography going. As a movie, not as an adaptation, I think it holds up.
I mean, if someone told me they wanted to make a 2 hour adaptation of AKIRA I would have laughed at them - because there is no way to condense that material in such a small space of time.