What is a good answer for an interview question "Why do you want to teach at this teaching university?" (when there are several others nearby) Assume there are 3-5 teaching universities near each other. What would be a good answer for an interview question : why you want to teach at this teaching university? 

To me I see no difference and it does not matter which teaching university to work at.
Let me elaborate on xLeitix's comment.  Applicants sometimes feel anxious about interview questions with hidden meaning or context.  The stereotypical example is "What would you say is your greatest weakness?", which is not a request to confess something awkward or damaging.  Instead it's a test of social competence, of whether the applicant can offer a smooth, natural response that sounds like it is addressing the question and avoids disclosing anything problematic without sounding arrogant either.  These sorts of questions are less common in academic interviews, so you can usually assume a question means more or less what it says.

In particular, this question is trying to gauge how well you would fit into the university and department.  Teaching universities can be really diverse in how they function, which students they serve, or what they consider their mission.  They are looking for someone who will participate enthusiastically and help make the department a better place, not just someone who is willing to teach there (or, worse yet, will feel bitter or resentful about not having found their dream job).

The worst case answer is "Gee, I don't know.  You have students, and I can teach.  What's not to like?"  That basically amounts to announcing that even you don't think you're a particularly good fit.  Your comments sound uncomfortably close to this, like you really don't care or see any relevant differences between these schools.  If that's the case, then you need to spend some time looking into them online or asking your friends or colleagues.  Unless you've applied to an extraordinarily narrow range of universities, I can't really believe they are indistinguishable.  And if they are, then you must have targeted this type of school intentionally, so you just need to explain why.

Austin Henley's answer provides a nice list of criteria you could keep in mind, and there are also big-picture issues.  Are these schools public or private?  How do they present themselves to the world?  Is there anything distinctive about their history, such as a religious or social mission (former or current)?  Is there any special focus, such as technical or liberal arts education?  What sort of student body do they serve?

There are no right or wrong answers here: one person might prefer to teach diverse and economically downtrodden students, while another might be excited about working with exceptionally well-prepared students from the elite.  What's important is that your answer should reflect some genuine resonance between you and the school.  If it sounds like you are saying something generic or canned, then it won't really help your case, but anything insightful or heartfelt could help.