Should I not apply to a PhD program when a Potential Advisor gives me a generic response? I have been sending emails to potential advisors for PhD programs, and the responses have varied from, You have an impressive CV, and I strongly encourage you to apply, to lets discuss future projects over skype. 

The "lets discuss projects over skype" is a no brainer. But the "impressive CV" response seems a bit generic, and am wondering if he wants me to apply just to have more applications? So finally, I have these questions:

If you are a potential PhD advisor, what kind of responses do you give students that you MOST want to apply to the program? Do you ever say, please don't apply here? Does this vary depending on the ranking of the institution? I tend to get the generic ones from higher ranked programs and the more personal ones from lower ranked programs.

Also, For people who have applied to Phd programs, What kinds of responses did you get and what was the outcome of your application there?

The primary motivation for this question is because there are many departments I wish to apply to, but realize applying to 20 programs would take up too much time.

Anyway, thanks for taking a look at my questions.
In managing responses, you should keep in mind the policies and procedures of respective departments. For instance, in my field, projects aren't discussed until after a student's been admitted, and the decision regarding advisors isn't made until after students enroll. So there's little productive reason for an advisor to discuss projects with prospective students, given the enormous time between the conversation, and when the student would start working.

In addition, keep in mind that professors are busy professionals, and have lots of demands on their time. For instance, the professor you've written to might be on travel, or have some ongoing commitments that preclude a longer answer.

Now, on the other hand, if you're submitting to an individual PhD position, and the professor will hire you "directly," then a generic response isn't so good, unless there's an indication that the professor would like to discuss things further. 

Finally, how generic a person's response will be will also depend on how generic or specific your initial inquiry is. If someone "cold calls" me, and "greets" me with "Dear Sir" or "Hello," and doesn't show any signs of explaining why I should consider hiring that individual, I am unlikely to respond at all, because why should I write a personal response to a form letter?