Can non-native teachers deliver proper language and pronunciation as that used by native-speakers?

Being native doesn´t mean that someone can communicate ideas clearly. Most non-native English teachers are well trained in their countries and can deliver good language training. Obviously, it is expected to have good pronunciation, but who can set up the standard of the ideal pronunciation, when it is so diverse among English speaking countries.  Accent is not a synonym of poor teaching, on the contrary, it may even be beneficial for languages learners to be expose to different kind of accents. 

A successful teacher should have an exceptional command over language. There is no doubt about that. You need a good language model. However, it is a mistake to assume that only a Native Speaker can provide it. Most renowned schools select successful candidates based on logical and measurable criteria which are independent of and irrelevant to being a Native Speaker or not. For example: Qualifications, teaching experience,Language proficiency, Personal traits.

It depends. It is unfair to generalize. I know many non-native teachers who do a great job. I also know many native teachers who do not do a great job. If the teacher is qualified and experienced, most probably they will perform well in class regardless of being native or non-native.

I think neutral and clear accent is more important than native pronunciation. The speaker should be confident and knowledgeable. 

Definitely can deliver.

The teacher obviously is qualified and can speak the language very accurately. And why I think they can is because English language even being native language for Americans, British and Australians are spoken very differently and with a different accent. So you might have a native speaker teaching the language but still the pronunciation is different everywhere.

So this native or not native does not make a difference.

Definitely!!

ESL teachers have excellent and extensive training before getting their accreditation and their university diplomas. Saying there's a perfect accent to teach English is like saying there are perfect people and all the rest are just ... all the rest. Worthless or useless.

Most native speakers I know, and they are plenty, are clueless when you talk about grammar, for instance. They show this gap when they try to learn a foreign language themselves. Nouns, verbs or even adjectives are words most of them reveal not to know the meaning of.

I wonder if it is even fair to compare an English teacher to an ESL teacher at all. Teaching English to native speakers is totally different from teaching ESL!!