3. St. Elsewhere
If I had actually watched St. Elsewhere when it was on, I would have been so beyond pissed at the plot twist in the series finale. Audiences have just spent six years of their lives watching a medical drama about the staff at a teaching hospital in Southie, pejoratively referred to as St. Elsewhere. Or at least, that's what they thought. But the joke's on them, because apparently St. Elsewhere never actually existed... it was all in the imagination of an autistic boy holding a snow globe. I can't think of a bigger F-U to audiences than that. To end a show on that note... well, you deserve all the hate mail you get.
How It Should Have Ended Well, anything would have been preferable. Anything other than "JK none of this was real."