Well, when it comes to home console video games, Kaizoku Musou is definitely the ONLY adaptation of the series in video game form. It covers more ground and feeling of the story than any of the other games. Now, if you were to ask me which is the best game that adapts the series in general it would be the newest PSP game Romance Dawn by the looks of it. Gigant Battle hardly tells anything about the story besides fighting in areas based on the series, it just has a bit of narrative the rest is just fighting.
Fixed your quote up for ya.