As a few other people have pointed out, it's really a high *conversion* that you want, with a high enough CTR that you benefit from a good quality score from Google (i.e. you pay a little less per click).

If you can get your visitors to take the action you want (buy a product, sign up for a newsletter, contact you for more information, whatever) at a high enough rate, then you can optimize the front end (ads and keywords) to improve click through (but hopefully without reducing the conversion rate).

For example, if I create an ad saying "Free Beer Delivered to Your Door", I'll probably get a pretty high click through rate. Maybe event 50 percent

But if the landing page for that ad is misleading (it's really some sort of offer like "Buy a case of beer, get one beer delivered free"), very few visitors will actually take any action, making the ad not cost effective, and my click through rate irrelevant.

So ideally you want:

1. A good, specific ad that disqualifies visitors (e.g. "Best prices on beer")
2. Is well targeted towards relevant search terms ("buy beer online" or "online beer delivery", but maybe not "free beer")
3. A landing page that converts well (makes it clear what they should do, loads quickly, is attractive and effective, etc., e.g. "Buy a case of beer today for 30% off retail, and get one extra beer for free. Free Delivery!".)