List to give to friends who don't read comics - stand alone works only - were not serialized first
City of Glass
Storeyville (of course I'm gonna recommend myself)
The Blonde Woman (was serialized online - but was composed as a complete work)
Watchmen, Maus, Love and Rockets, Jimmy Corrigan, Dark Knight Returns, Batman Year One, Kings in Disguise, From Hell, It's a Good Life If You Don't Weaken, Ed The Happy Clown, David Boring, Like a Velvet Glove, Glorianna - most well known classics of North American comics were serialized or appeared as single issues in a continuing series. This makes it hard for the new reader to jump in if there are recurring characters - like Love and Rockets. I also think serialization changes the work - the planned story breaks - the issue breaks - the work is different if it is released all at once. I think it's very tough to come up with a list of "stand alone" comics to recommend to new readers.