I'd say the line is where ever you choose to draw it, just don't be surprised if others draw it somewhere else. I've read more than a few books that were a little slow to start in the first couple chapters, but ended up being among my favorites. I see no reason why the same is impossible for comics, and I doubt I'm alone in that.
Surely some books improve as they go, but some people here are implying it's wrong to expect a book to wow them in the first issue, and it seems absurd to suggest that people need to wait and spend more money until they can enjoy it, because, you know, that might never happen.
There are people that still claim that bendis sells books on name alone. They tend to gloss over the fact that the characters and artists have a stake in those sales. I'm thinking marvel does too, hence the continued high profile projects he gets or they don't want to show that an "architect" is not as good as the hype.
That's all you really should give a book is one issue to impress or hook you. You shouldn't have to buy 3 issues before the story actually starts rolling. Comics should be written to where anyone should be able to pick up any issue and be hooked enough to pick up the next and eventually interested enough to pick up back issues of the book.
Regardless of the writer's intentions, comics are generally sold in single issues. A single issue is its own product. If it's not worthwhile in and of itself, why invest more money?
Yep. Especially not when a company like Marvel is charging an average of $3.99 an issue. Others might not mind doing it, but I refuse to wait around for a quarter of a year and tie up 12 bucks of my money in the process just on the off chance that a book MIGHT finally grab me.
And it's not like it's impossible to write a good first issue that hooks you in. Uncanny X-Force did it. The relaunch of X-Factor did it. Some people thought Uncanny Avengers succeeded.