Well, it can be, but there is a lot more to it than just the number of comments.
It is true that comments are vital for successful blogging and when there are no comments, it is a sign that something is done wrong.
But, have you ever thought about which post made your reader subscribe to RSS or follow your twitter? Which post made your readers think “this guy knows what he’s talking about” or “I definitely want to see what she says next” or simply “that’s awesome, I want to read more!”.
These readers are important to you, because they “marked” your blog and will get back to it in the future, even if they don’t say it out loud right now.