I think a lot of it depends on where Guild Wars 2 fits in your gaming life.
For example, I am an extremely jaded gamer, and therefore have very few new games that I like (so far only games I like this year are Portal 2 and Terraria). As such, I also watch very few games closely since most of them get a "meh" or "bleh" reaction from me, and often those that would likely interest me due to history fall short due to something I dislike (Heroes 6, for example, despite my love for 2 and 3). Because I watch very few games, this makes getting games on my watchlist extremely hard, yet makes competition ON that watchlist surprisingly light.
With that in mind, Guild Wars 2 managed to grab top spot on my watchlist, and KEEP that spot, despite all of my annoyances with much of the popular competition in the genre. Also, because I haven't bought any (major) games since Portal 2, I currently have PLENTY of room for a game to play!
There's a lot of factors as to why a person does or doesn't get tired of waiting for a game, but I feel the biggest factor is competition. If there are a lot of games that a person already is playing, already plans to play, or is watching, any of these things can crowd out any single game that the person is watching. For example, in addition to GW2, I'm waiting for Skyward Sword and Last Guardian. Skyward Sword will likely grab my attention near the end of the year, but information gathering has essentially hit a peak. Last Guardian, on the other hand, has its information come in waves, and therefore lots of lulls in information. Thus, hunting for information for this one doesn't amount to much. In the end, it's extremely easy for me to focus all my attention on Guild Wars 2, since I have few games I'm playing, one game that I've hit saturation with, and another game that has bursts of information with long downtimes.
Plus, Guild Wars 2 is unique in that it is trying to redefine its genre in some big ways, so it's held my attention easily.