Ok let me put my criteria.
1. his knowledge of Quran and Sunnah
2. His practices on Quran and Sunnah.
This is regarding piety. But I have high respect towards any muslim who recites kalimah. Wallah.
Also, I have more respect towards a person who is not pious but his services help muslim community than a person who is pious but limits himself to his personal ibaadaath.