Reddit mentions of Lone Wolf and Cub, Vol. 1: Assassin's Road

Not sure you're going to find anything better than Watchmen. However here are a few thoughts...

• [Miracleman] (http://www.amazon.com/Miracleman-1/dp/B002D9MQS0/ref=sr_1_7?s=books&ie=UTF8&qid=1342221492&sr=1-7&keywords=miracleman). This is also by Alan Moore. One of the greatest superhero stories ever told. Alan Moore started it and Neil Gaiman came close to finishing it, but never did due to copy-write issues.
  
• [Ronin] (http://www.amazon.com/Frank-Millers-Ronin-Miller/dp/0930289218). By Frank Miller. Combines Sci-Fi and Samurai comics. I don't really understand the ending, but the journey is great.
  
• [Lone Wolf & Cub] (http://www.amazon.com/Lone-Wolf-Cub-Assassins-Horse/dp/1569715025). Without a doubt the most epic comic book ever written. Probably the most influential manga that most people have never heard of. A true work of art. This is Frank Miller's favorite manga. Also, an influence on Quentin Tarantino! The authors are Kazuo Koike and Goseki Kojima. Spans 26 volumes. By the end you will feel that you have graduated with a degree in ancient Japan (well almost!). Poetic, violent and a little spiritual (at least if you like Zen Buddhism).
  
• [Maus I and II] (http://www.amazon.com/Maus-Survivors-Father-Bleeds-History/dp/0394747232). This is Art Spiegleman's conversation with his father about the Holocaust. It is part survivor's tale and part story of a son trying to understand his father's history and also his own.
  
  I heard today that all good stories should ask the question "who am I"? All 4 stories I have recommended do that.
  

Good concept, look forward to seeing your progress. If you need some inspiration or similar material check out Lone Wolf & Cub manga. Dark Horse published the uncensored versions in original format and are outstanding.
Authors Kazuo Koike Goseki Kojima thoroughly researched items for era accuracy and their attention to detail and cultural nuances are spectacular. The footnotes help us understand details within the stories.

Good luck!