The official Star Wars blog says the Japanese manga adaptation of the first three Star Wars movies is light years better than Marvel Comics' original adaptation. To hammer home how flawed the American version was, here are some comparisons of how certain scenes appeared in the U.S. and japanese versions.
According to the Star Wars site:
[I]t's truly an unfair comparison to gauge how well Marvel Comics originally adapted the classic trilogy films against how Japanese artists did the same. The deck is definitely stacked in manga's favor. For the Marvel adaptations, produced during each film's post-production period, the artists had not seen the films — they were working merely from the script, with some key photography and maybe some concept art... Japanese manga has a much more flexible format and page count to accommodate a more deliberate and varied pace of storytelling. Since the Japanese manga versions did not come out until 1997, the artists benefited from years of studying the flow and dynamics of the movies.
It's not just the problems of pacing and available space - while Marvel's 22-page limit for each issue reduces the destuction of Alderaan to one panel, the manga spends six pages on the same event - but also of editorial restrictions: Vader cutting off Luke's hand is shown in all its gory detail in Japan, but American audiences find a piece of machinery suspiciously in the way.
But as much as the manga adaptations improve on their American ancestors, they do lack the wonderfully overwritten exposition of the Marvel books. A picture may be worth a thousand words, but when those words say things like "Then, the darkness swallows him. Deep. Vast. Unnatural in its totality. And with the sudden hiss of a lightsaber igniting... Luke finds it conceals far more than he ever dared imagine! wouldn't you rather have the words themselves?
Turning Star Wars Japanese - Manga Scenes Done Better [Star Wars.com]