Here is in its entirety the 1966 animated Grinch Cult Classic special. Sure this special may not have what your insult to Dr Seuss I mean so called "definitive" 2000 live action film had (Like Jim Carrey dressed like Oscar The Grouch's deformed twin, unnecessary origin stories (When did The Grinch ever need one?! That's like giving Gumby an origin story. Eww), guys kissing dog's butts and all sorts of trash that would make Ted Giesel toss in his grave, but in the half hour it ran, it had more for it than the other 2 iterations ever will: Solid animation from cartoon legend Chuck Jones, the voice talents of Boris "Frankenstein's Monster" Karloff narrating and voicing The Grinch, June "Everybody's Generation" Foray as Cindy Lou Who, and Tony the Tiger Original himself Thurl Ravenscroft singing the Grinch song. Overall 5 out of 5. The other two iterations can teach their grandmothers to suck eggs! 

The Grinch Original 1966 > The so called "definitve" Grinch Live Action

the best christmas specials are the short ones

and on that note, the garfield christmas special has become underrated too.

Speaking of, fun fact: Eons before he went off on his own and got famous doing shows like Garfield and Friends and Bobby's World, doing animation contracting for The Simpsons, and doing all those Garfield specials as well as that Turok film (that was based more on the original comic book of the 1950's. Today, most of our generation only knows Turok as a character who was on games for the Nintendo 64 but once upon a time, the boomers and Generation X knew him as a comic book character) and to a lesser extent, that stupid Grandma Got Run Over By a Reindeer film, Phil Roman worked for Chuck Jones. He was one of the animators who worked on The Grinch Original. Neat eh?

And not to mention Ted "M****f****n' Dr Seuss" Giesel himself involved with the special (but then so did most of the Dr Seuss specials with one exception: See his posthumous release Daisy-Head Maizy for reference)

Ted Giesel + Chuck Jones + Phil Roman (Years before he made a name for himself) + The voices of Frankenstein's Monster, Natasha Fatale/Rocket J Squirrel/The Wolf Mother on Mowgli's Brothers/Ma Beagle/Pretty much Everybody's Generation, and Tony the Tiger = Ultimate Fan Person Moment

I actually enjoy Halloween is Grinch Night a tiny bit better than the Christmas special. Go figure.

same here vapor, it's far more underrated imo.

I don't know where you're getting this "definitive" business from, but I agree the 1966 animated special is the best version of the Grinch.

"and on that note, the garfield christmas special has become underrated too."

I never thought of How the Grinch Stole Christmas or the Garfield special as underrated.