Comic books are an extremely visual medium. Concept art is about as direct a translation as you may find in going between comics and film because... well... concept art is still drawings, sometimes even done by the comic book artists themselves.
Physically fabricating these things is another matter entirely. Going from 2D to 3D is another world. Fabrics, shadows, flexibility, and believability are all huge factors. Also, you have to keep in mind the origins of the costumes - could a high school kid with no prior sewing expertise really craft a $10,000, state of the art suit, in his garage? Doubtful.
Most of the time, especially in the last 15 years or so, comic book adaptations fulfill our wildest dreams! We get to see characters we've known since we were kids, whose exploits we've grown up reading, come to life before our very eyes! It's the very essence of magic.
These are the other times.