An over-the-top storyline that doesn't pretend to be a serious drama?
Questions that are actually answered? Wait, is this really the same writer as Monster? Sure, the twists and turns and general flow feel the same, but my God, he actually did it right this time.
Instead of a boring, pretentious slog with no point you have a grand adventure spanning decades.
Instead of the villain being a young sociopath with inexplicable resources and power, it's a pervasive cult that steadily grows in power throughout the series.
Instead of the main character being some kind of masturbatory Japanese power fantasy, he's just a total bro who wants to rock out.
Not every element of it is perfect. Naoki Urasawa is almost definitely an improv writer, he just riffs as he goes along with no ending planned. He's insanely good at that, but the cracks show. Most relevant mysteries are sufficiently wrapped up, but sometimes in a lazy way. The major series-wide mystery that is ultimately resolved in the sequel series, 21st Century Boys, is most definitely not perfect, but infinitely more satisfying than Monster's ending.
And the subject matter simply lends itself to Urasawa's jazzy improv writing a lot better than Monster's. Tenma is confined dramatically after the opening events of Monster and his journey is not as open-ended as Kenji's. Johan is a laughably unrealistic character with completely unexplained power and wealth. Contrasting that, 20th Century Boys goes through a lot of flashbacks and different time periods with an almost ensemble cast, allowing for that jazzy improv writing to lead the series in whatever direction Urasawa felt that week. Friend, the cult leader and central antagonist, is a much more believable villain than Johan simply due to the fact that his identity is completely hidden, meaning he could be any person or number of persons.
20th Century Boys also benefits from a persistent story that continually builds on itself. While Monster had an underlying mystery that was solved with little hints here and there, it was a mostly episodic series with Tenma wandering Europe helping everybody in his path. 20th Century Boys acts more like a typical serial with major arcs.
There are also some simply insane, incredible, unforgettable moments in this series, none of which I can even mention without spoiling them. I'm very happy I read this series before Monster as I likely never would've touched it otherwise. Where Monster disrespects you by building up to its conclusion and then completely doing a 180, 20th Century Boys has various moments that require great audience trust and Urasawa does not disappoint. That's as far as I can go without getting into spoilers.
I didn't intend for this to become a compare/contrast review, but I guess I just hate Monster so much and love 20th Century Boys so much that I couldn't help but think about it constantly.
