Little Noboru from the 1998 GTO drama, Oguri Shun, has grown up to take on the role of our favorite samurai lazy-bums, Gintoki Sakata! I've also seen him as Shinichi Kudo from the live action Detective Conan movies, but his acting chops have definitely improved here in Gintama.
The Benizakura Arc was the first major story arc for the Gintama anime, and it has now been made into two movies, an animated retelling and live action. Personally, I feel like Benizakura isn't the most amazing arc compared to the later ones (especially the Shogun arc), but it's understandable that as a live action film that's seen by many newcomers, this is the most accessible story arc for them. There's a lot of familiar humor for old fans of the anime as well, along with some new ones. In particular, the meta-humor stands out the most, including self-mockery about how the movie needed to appeal to newcomers as well and thus requiring an obligatory origin story at the beginning. The funniest jokes I found were the references to other anime and the characters' fear of being sued for copyright infringement, including a hilarious cameo by Nausicaa.
Unfortunately, the humor can fall flat sometimes in this live action format. Humor in anime (or just animation in general) rarely works as effectively as live action. When you try to imitate the kind of exaggerated comedy in anime, it can come off as lame and contrived. For example, the (lackluster) special effects of Shinpachi being punched stand out more than the unfunny joke itself, and that gag got old after the first time. Some of the characters attempting hyperbole (like Tetsuya Murata shouting) also look really awkward in real life. These comedic moments just don't work well outside of anime, and that's the same problem I had with Scott Pilgrim when it tried to emulate such cartoonish effects in live action. Henpeita Takechi also looks nothing like his anime counterpart because of his eyes, but that's something live action is incapable of adapting, so that's inevitable (though I'll bet Marvel Studios would go above and beyond to keep such aesthetic details faithful to the source material in some shape or form; shame that Japanese studios couldn't do the same).
Some of the actors do manage to pull off their gags relatively well. Oguri's "straight man" retorts work well enough (though definitely never surpassing the brilliant Tomokazu Sugita). Nakamura Kankuro as Kondo was not bad, but that had more to do with him being a good sport, letting himself get covered in honey (or whatever that golden sauce was) than his acting chops. The other casting choices, however, were kinda iffy. Domoto Tsuyoshi as Takasugi just looked weird, as his face was too chubby for the role, and his attempt to act stoic just came off as dull and lifeless. Also, why is Shinpachi shouting all the time? And why is he so violent in this movie? Totally out of character.
And finally, we have to talk about those cheap special effects. I don't know many anime adaptations in Japan have such low quality CGI. The Japanese just don't seem capable of matching the Americans in realistic-looking CGI for some reason, and Gintama live action is no exception. They even used blatantly fake masks in place of the Amanto... I wonder if that's intentional as some form of satire, but I highly doubt it since they didn't address these cheap props.
Finally, there isn't that much important information about the Gintama universe to make this a must-watch for newcomers. The sword-fights in live action do look cooler than the anime, that's the movie's one saving grace, but other than that, it's not really an impressive retelling for you to go out of your way to watch this. Watch the animated telling of Benizakura instead - it has the awesome "Bakuchi Dancer" by DOES playing in the final fight whereas this live action version just has some forgettable score.