I think these days even 3 episodes to "get good" is a possible death sentence.
Back then networks were more willing to give low rated shows more of a chance even if their first seasons were lowly rated. It's swim or sink with shows these days. One of the reasons why I usually wait until I hear a show has gotten a second season before I start watching.
ENT didn't really have this problem. Its ratings started out very strong and just fell.