How the voting was tallied
I had a very loose definition of voting. I allowed for comments to vote on multiple titles. If someone wrote "I would chose xxxHolic over all of them, but Fairy Tail is pretty good too" I would give a vote to both xxxHolic and Fairy Tail. However, if many titles were listed but Parasyte was listed as the "best ever" I would only give a vote to Parasyte. This seems pretty fair since xxxHolic is the clear winner despite my lax rules on voting.

xxxHolic - 17 votes
Fruits Basket - 7 votes
Death Note - 6 votes
Parasyte - 5 votes
Scott Pilgrim - 4 votes:
--everything else received 3 votes or less.

For no other reason than my copy of xxxHolic volume 1 is at home instead of conveniently at the office where I could pass it on to Catherine, I'm going to leave the voting open for one more night. I have little doubt that xxxHolic will remain the clear winner tomorrow morning. But surprises are always fun.

THANK YOU THANK YOU THANK YOU for all of your suggestions!
You all had a plethora of wonderful titles for me to broaden my own manga horizons (being relatively new to the genre myself). Here are the ones I plan to check out very soon in no particular order:

Death Note

You said it is, "a great psychological thriller with elements of horror." And that's pretty much enough to sell me. That and it comes in second for WRITE-IN votes, so it must be good. (the anime looks pretty sweet too!)

Viz Media says, "Light Yagami is an ace student with great prospects - and bored out of his mind! But all that changes when he finds the Death Note, and notebook dropped by a rougue shinigami death god. Any human whose name is written in the notebook dies, and now Light has vowed to use the power of the Death Note to rid the world of evil. But when criminals begin dropping dead, the authorities send the legendary detective L to track down the killer. With L hot on his heels, will Light lose sight of his noble goal... or his life?"

Cromartie High School

You said it is, "the best comedy manga that doesn't get lost in translation." I thought that sounded fun. When I searched for it and saw the amazing covers ... I wanted to read it today. For the art alone!

PW says, "Some jokes translate well; some don't. The first volume of Nonaka's Japanese school comedy (which has also appeared in anime form) has a lot of both kinds. The setting is a high school for the toughest boys around, where everyone's always trying to prove how bad they are and figure out who's strongest among them. But the students are also not the swiftest bunch, with the exception of this story's more-or-less normal protagonist, Takashi Kamiyama. Hijinks ensue--mostly in the form of six-page blackout sketches that end with an all-but-audible rimshot."

Muhyo and Roji's Bureau of Supernatural Investigation

You said it is, "Harry Potter with more action and less school. No gore." (Ok, so actually Nearly Mello said, "it is a very cutesy series that I find myself salivating for the next volume of. The art has a lot of flair, and it's like Harry Potter with a lot more action and less school." but I thought I would pare it down a bit for this. Oops)

Viz asks, "Are you a victim of unwanted spirit possession? Is there a ghost you need sent up and away...or down to burn for all eternity? If the answer is yes, then you need Muhyo and Roji, experts in magic law. Serving justice to evil spirits is their specialty. When the ghost of a tormented schoolgirl starts terrorizing subway passengers, can Muhyo and Roi resolve the paranormal crisis before it totally derails?"

Emma

One very thoughtful post by Beppo says, "Emma's a bit different, for a manga, in that it takes place in Victorian England, and therefore the reader doesn't have to know anything about modern Japan. The storyline is fairly slow-paced, there are no supernatural elements, no horror or gore...it's really just a thoughtful, gentle little look at class differences and romance in the Victorian era." Since Pride and Prejudice is my favorite book, I thought this was a manga retelling of Emma. However, I am still inclined to read it and love it even if it isn't an Austen Manga.

Amazon says, "Emma tells the story of a young Victorian/Edwardian maid and her forbidden romance with a gentleman from a large merchant house whose family has aims for him that are much higher than she. Volume one of the series contains the first seven chapters of the eventual fifty-two and focuses on basic introductions."

Fruits Basket

You voted it third (2nd for the write-ins), and said, "one of the sweetest and funny although a little dramatic love stories found among growing up and moving on leaving the past behind but not forgotten." Although a jumble of effluence on that one, it sounds pretty good.

TokyoPop says, "Tohru Honda was an orphan when one day fate kicked her out of the house and on to land belonging to the mysterious Sohma family. After stumbling upon the teenage squatter, the Sohmas invite Tohru to stay in their house in exchange for cooking and cleaning. Everything goes well until she discovers the Sohma family's secret, when hugged by members of the opposite sex, they turn into their Chinese Zodiac animal!"

Also, to see the comments where the voting took place, and to hear what Catherine had to say about my synopsis ...
My First Manga: First Cry for Help
My First Manga: Meet Catherine