I find that games that generate that level of pre-release euphoria never live up to expectations. Nine times out of ten they end up being a giant let down at release. This is not because they are bad games, it is all about perceived relative value.
For example, my biggest at release let down of all time was Spore. I remember watching the initial game play demonstrations in 2005 and saying to myself, this is going to be the best game ever conceived of by a human. The most complete simulation of life you could buy. Fast forward three years to its release in September 2008, and I was one of the first in line to buy it. I took it home and was disappointed by what I found, a disjoint collection of loosely tied together mini-games and editors culminating in a long and pointless grind in a space ship. I expected one thing, and got another
I want to emphasize that it was disappointment. It wasn't that the game was actually that bad. Its editors were fantastic creation tools and I still have not seen their equal in other games. The procedural generation systems it used to extrapolate walking patterns based on limb and spine configurations astounded the computer scientist in me. The user content sharing system was innovative and encouraged people to make interesting creatures and building so that everybody else could discover them somewhere in thier galaxy. Let us not forget then encountering the inevitably phallic creatures and buildings that others created in your own galaxy.
The big issue was that I had three long years to take what I saw in early alpha, and massage it in my mind. I created unreasonable expectations that no game could ever live up to. Ultimately it is my own damned fault that I felt let down. I built it up in my mind based on sparse and incomplete information. However, in most cases it is also the fault of the industry. They generate hype on purpose because everybody knows that hype sells copies. If you can build enough pre-release hype you will have a successful game at release, financially anyway. Its just good salesmanship.
Share your biggest let downs in the comments below. Perhaps it can become a great big therapy session taking place in the highest echelons of first world problems.