Over in this thread it has been noted that Pratchett fans have some wildly divergent views especially on the later novels. So why not poll on it? Which three Pratchett novels are your favorite and which three are your least favorite?
Favorite three:
[ul]
[li]Wyrd Sisters[/li][li]Night Watch[/li][li]Good Omens[/li][/ul]
Most Disliked:
[ul]
[li]Fifth Elephant[/li][li]Monstrous Regiment[/li][li]Thief of Time[/li][/ul]
Most Liked:
Hogfather
Good Omens
Small Gods
Least Liked:
The Colour of Magic
Equal Rites
The Lost Continent
Favourites…
Nightwatch
Going Postal
The Truth
Least Favourite…
The Colour of Magic
(I have not read any others that I dislike. And of the ones I have read it’s impossible to pick the ‘worst’ apart from CoM)
Favorites:
Night Watch
Hogfather
Small Gods
Least favorite:
**
Monstrous Regiment** (by far)
Pyramids (except Teppic’s Assassin training)
Equal Rites (the early Granny is…wrong. As is Esk.)
Good Omens is not a Pratchett novel, and therefore isn’t included on my list of faves.
Um… It is a Pratchett Novel (And Gaiman)
What it isn’t is a Discworld novel. And the OP didn’t specify Discworld.
Yep, mainly so people could toss in Good Omens or Nation or complain about Strata (with squirrely British spellings or otherwise 
).
GO wasn’t written by Pratchett. It was, as noted, written by Pratchett and Gaiman. Which makes it outside the OP as written. 
Favorites:
Going Postal
The Fifth Elephant
Sourcery
Least Favorite:
Monstrous Regiment
Eric
Those were the only two I finished and didn’t immediately want to reread, so… they’ll work.
Semantics. If it was written by P and G then the statement “wasn’t written by Pratchett”, to my mind, is false.
It was written by Pratchett.
And it was written by Gaiman.
If you had said “wasn’t written exclusively by Pratchett” then I’d forgive you, but then the op didn’t use the word ‘exclusive’ anywhere.
Let’s not fight. Let’s all come together in out mutual enjoyment of Good Omens. 
Most Favorite:
Night Watch
Lords and Ladies
Small Gods or **Going Postal **(can’t decide).
Least:
Eric
Monsterous Regiment
That Australia one, or maybe Carpe Jugulum.
Well, My two favourite authors (excluding David Mitchell) are TP and NG so this is like the perfect book. They need to do more collaborations.
Favorites:
Small Gods
Lords and Ladies
The Fifth Elephant
Least Favorite
Thud
Eric
Making Money
Most favourite:
Night Watch
Thud!
Going Postal
Least favourite:
Eric
Soul Music
Colour of Magic
FWIW I liked Monstrous Regiment, the Tiffany Aching books and Nation. Good Omens has a special place in my heart for the version of the “Grand Old Duke of York” that Nanny Ashtaroth sings…
Tough to say - it has changed over the years, but at the moment
Favorites:
Going Postal
Hogfather
Lords and Ladies
Least favorites:
Making Money
Eric
Interesting Times
Also, Mr. Cake wanted to mention his:
Favorites:
Guards! Guards!
The Fifth Elephant
Wyrd Sisters
Least Favorites:
Moving Pictures
Pyramids
Eric
Favorites
Small Gods
Guards! Guards!
Pyramids
Least Favorite
Moving Pictures (a big disappointment since it had so much potential)
Reaper Man
Sourcery.
Favorites
Thief of Time
Going Postal
Men at Arms
Least Favorites
Maskerade
Moving Pictures
Sourcery
Favourite
Maskerade
The Truth
The Last Continent
Least Favourite
Night Watch
Fifth Elephant
Carpe Jugulum
My tastes seem to run counter to the majority’s. Story of my life.
I just can’t narrow either category down to three. There’s four of each that instantly popped into my head.
Favorite:
Small Gods
Night Watch
Going Postal
Thief of Time
Disliked:
Monstrous Regiment
Equal Rites
The Color of Magic
The Light Fantastic (the entire Rincewind serious actually, except the scenes with Ridcully and the other senior wizards)
I’ve only read 8 or 9 so far, so I don’t have a big pool to work from, but mine are:
Top 3:
Guards! Guards!
Men at Arms
Hogfather
Lords and Ladies (I can’t count, you know)
Bottom 3:
The Color of Magic
The Light Fantastic
Small Gods (and I don’t know why. I should like this book!)