The Legend of Zelda: Skyward Sword and The Dark Knight Rises. And in both cases, I was not disapointed :D

GTA:San Andreas- I was a huge fan of the of the series back then (I still am, but not quite as much). When I found out the game was going to have not just one, but three cities, my mind was was blown. The whole idea of being able to explore a fictional version of my home state was awesome.

As for movies, I would say the Simpsons movie. It is still my sentimental favorite tv show and when I found out they were going to make a movie I couldn't believe it. While the movie was pretty good, I was a little disappointed by it.

Mario Galaxy and it became my favorite game of all time! Yup.

Pokémon X and Y
and... Godzilla

Only a few times.

-Twilight Princess
-Star Wars prequels
-Metal Gear Solid 4 (For a long time, I considered MGS3 the single greatest game, ever)

Sadly, none of them lived up to expectations (But Loz:TP came close!).

At this moment
Avengers the age of Ultron,
Smash bros for WII U mainly due to the megaman trailer.
Bloodborne mainly due to the anouncement trailer

Game - Final Fantasy VII

I remember telling my mother it was the only thing I wanted for Christmas that year. It was in short supply and she wasn't able to get it. She asked the clerk at the gamestop (or equivalent back then) for something comparable so I got fucking Myst for Christmas. Then, a friend let me borrow the game one disc at a time. This naturally led to me only playing the first disc as he never got around to giving me the second and third discs. Years later I finally played through the whole game and was woefully disappointed by it.

Movie - Lord of the Rings: The Fellowship of the Ring

Friends and I were beyond hyped for this one, glad it didn't disappoint like FFVII did.

And, because another poster mentioned books:

Book - A Memory of Light

I was hyped for this strictly so I could finish the Wheel of Time and never have to deal with it again. That counts right? :)

Episode 1 was the first and last time I would ever be incredibly hyped for a product of any kind.  It was such a great lesson in tempering expectations.  Not even the bad-ass Darth Maul scene (before he's chopped in half) at the end could salvage that rubbish.  And then to find out that people actually liked it...it was a sobering day and one in which I definitely felt like I had stepped into the next generation as kids still love episodes 1-3.

I watched the originals as a kid (the first two on TV, though) and the last in theaters.  I still like the prequels because it's fun for me to see what they're building towards.  Far from perfect but I enjoy them.  I have a big Star Wars marathon session a couple of times a year and I like how it builds towards the "good ones".  Doesn't change the fact that I fell asleep in the theater the first time I watched Episode I, though.

Kingdom Hearts 2. Kingdom Hearts 1 was an unexpectedly amazing game, to me. A threw so many hours into that game. First one I put in over 90 hours.

So when I heard about a sequel, and saw screenshots in EGM and Game Informer, saw the commercials, etc. my hype was through the roof. Now, this is when I was 16 and didn't have a job. I still managed to get the game less than a week after it launched, rushed home, and immediately played it for 6 hours straight and I loved every moment of it