Some people get excited after they have answered an ad in the paper. They know this is the job for them.
Do not be surprised if you answer thirty or fifty ads and get no interviews. Your resume is with perhaps thousands of other responses. What's more, your resume is not being screened by the hiring manager.
Chances are, your cover letter and resume will be screened by someone like a twenty year old I met. She reviewed resumes on behalf of blue chip companies, screening thousands of professionals and managers in the $40,000 to $100,000 range. She decided who would get interviewed.
This young woman was good at her job, and often took a personal interest in the people whose resumes she saw but she was only twenty years old. Writing a cover letter to "intrigue" or strike a responsive chord in her wouldn't have worked.
While intrigue, subtlety, and personality may work in direct mail campaigns and networking, stick to the basics in answering ads. If the ad asks for specific qualifications and experience, highlight those areas from your background. Respond point by point to each item mentioned. Show how you have everything they want. Keep your cover letter crystal clear. Remember, the reader of your letter may be twenty years old. If you don't fit exactly, you will probably be screened out.
If an average ad in The Wall Street Journal or The New York Times gets a thousand responses, you have 999 competitors. Answer ads (I believe in doing everything to help your job hunt), but be clear and to the point.
If you qualify for the job, make that clear by following the format of the letter on the following page. If you do not qualify, use the paragraph format used in networking cover letters. If you don't get in by responding to the ad, network into the company or contact someone there directly (not the person mentioned in the ad).