Reviews are usually pretty high and it seems to me people buy into the hype pretty easily.
I guess when you spend 70+ millions on a single project, you use every trink in the book to sell it, and i wouldn't expect otherwise, but as more experienced gamer you get to read between the lines.
That is not to say that you can't get excited or hyped for a game, of course.
I didn't consider the limits of software or games until I had played *a lot* of different games -- and I don't think the people who don't game a lot, or take games as seriously, know about, or even consider the limits in terms of content and so forth.
Especially not when all publishers and developers imply, or even directly promise stuff that supports their assumptions. I think people just chalk the lack of those things in the actual games up to either budget, lack of time or inexperience, and continue to dream about vast, vivid worlds with few limits.
I think the majority of people know that there are tons and tons of games out there, and that the content-limit in some games don't necessarily apply to other games.
But the fact is, there is indeed an approximate limit to the amount of content or stuff that is possible to add to a game.
MMORPG's are much bigger than single player games because of the constant revenue stream, and constant updates. Not to mention that most of them have lots of procedurally generated content, and are very, very barren, and the majority of quests are extremely basic -- but gets away with it cause of the player-to-player interaction and experience.
Every game with a world over 20ish square miles tend to have lots of procedurally generated content as well, such as the Just Cause series (Exploration is kind of boring since there is little to no variation.)