It would be tough to narrow it down to just one, but I could probably bring it down to a Top 5:

The Dark Knight Returns
Watchmen
Wanted
Batman: The Long Halloween
One of the Astro City books (maybe Family Album?)

I'm SOOO glad that not just one but TWO of my top 5 graphic novels are getting the big screen treatment in Watchmen and Wanted; I know the two Batman books will never happen, but if we can just get some Astro City action at the movies, I'll be estatic!

First one to come to mind: KINGDOM COME.

I liked that Busiek and Woods Superman TPB with the Auctioneer. Really fun stuff.

My favorite GN of 2008 is Craig Russell's adaptation of Neil Gaiman's Coraline.

I've always thought that there were graphic novels and there were TPB's. Are TPB's now conisdered GN's?

When I think of a favorite GN,it's the She Hulk GN by Byrne and inked by Kim DeMulder. That had some of the most erotic She Hulk art I've ever seen. Great art, story and it took place in current marvel time when she was in the FF. There were also ramifications that happened in the GN that affected her status quo which carried into her character while in FF and was brought up again in her own series while Byrne was on that title too.
Specifically:
Spoilers:
Something happens in the GN that prevents She Hulk from ever becoming Jen Walters again. She will always remain in that form. Reed Richards confirms it. Luckily she likes being in that form so no big deal.
Years later in a special Xmas issue of She Hulk, Jen was granted a wish from an earlier plot device and she used it to become Jen Walters again. A moving story actually.

With people writing for the trades, I consider many TPBs graphic novels, now.

I'm of a mind that, it's only a GN if it was originally printed that way and not serialized.
So as good as Watchmen is, it's a TPB.
It was written to be read a piece at a time. and I think it still works best that way.
So my favorite comic book GN would be Death of Captain Marvel.
And non-comic book would be Wrightsons Frankenstein.

Of what mind are you about most of the longer works of Charles Dickens?

Also, are the various hardcover editions of Watchmen also TPBs?

I think a better way* of judging whether a work is a GN is not so much how it was first published, but how it was conceived by the creator(s). WATCHMEN is obviously conceived as a single story (albeit probably with the chapters in mind). I definitely consider it a graphic novel (which is to say, basically a novel-like piece of graphic storytelling).


*Better, but not necessarily perfect.

So you're saying if it's in hard cover it must be a book?
Watchmen was written as one story, but formated and paced for serialization.
Dickins work could be the same.