In terms of hype, The Avengers I'd say is probably one of the most hyped but also probably not the most hyped - I think it would be hard to pin down the most hyped film of all time due to shifting demographics and media vehicles although I'll note a few other possibilities.
The Avengers did have a crazy built up of expectation over a number of years/films which probably is fairly unique - although given the relatively average (in blockbuster terms) performance of the other movies such as Thor and Captain America the true impact of this I think is being over exaggerated. For sure it is among the more hyped films particularly in terms of target audience awareness prior to launch - although where it falls a bit short is awareness outside that demographic - i.e. a whole ton of people clearly have little idea about it other than another summer movie with some comic book characters.
From memory, in terms of hype, if I had to try and pick a film it would actually be The Empire Strikes Back. Star Wars had been huge of course - much bigger than The Avengers or The Dark Knight today and just behind Gone With The Wind in domestic performance - and had much, much more cultural impact than either of those films.
As you can imagine the build up and interest in Empire was immense at the time, just enormous and beyond target audience demographics - in terms of prior to release interest and then desire to attend the launch I really can't remember anything bigger right up to the release of The Avengers and yes considering the imminent release of The Dark Knight Rises.
I't's also worth considering that, at least in US, the largest films from say 1970 forward are easily Star Wars, Jaws, Exorcist, Titanic and ET. All of those saw more interest (if you adjust for inflation which you have to if you want to compare them) and all of them had far broader media coverage (post release for sure) and cultural impact.
But the Avengers is a lot of fun and wildly successful - and given I think Joss has had a really unlucky run over many years as a very talented guy it's really nice to see him knock it out of the park like this. The film is like the best candy floss you can buy - and I mean that as a compliment.
To this day - despite my dislike for the prequels nor how Lucas handled the franchise IP - I can understand why the pressure of delivering Empire was apparently almost too much for Lucus to manage.
Try to be reasonable... its easier than you think...
