As an actor...beyond publicity stuff, this is just the way that a lot of actors express themselves. Everything is the best, most exciting, most rewarding transformational thing ever. It's just sort of ingrained in an actor, to find something positive about what you're putting so much effort and emotion into. Part of that is "promotional", you want people to be excited about the projects you're in, and this is even taught in acting schools, but many actors also tend to have positive attitudes, and this is the rhetoric they often use. Because of that, I don't see the point in questioning the legitimacy of everything someone says just because they're supposed to portray their product in a positive light.
Of course, while a lot of them may be great actors and actresses, in my experience, many of them don't neccessarily know good writing from bad, a whole lot about story structure, etc. Which is part of the reason why you see great actors choosing lousy projects, even when there's no major financial boon.
