I think he embodied the dumbledore from the 3rd book on. Richard Harris was perfect for the very young novel, easy-going-soft-whisper-grandpa. But Harris would have never pulled off the ministry fight with voldemort. Both actors pulled off what they needed to.
Aside from the goblet of fire angry line, you know which one. He was one of the best parts of the series. His delivery especially in prisoner of azkaban, after he shuts the door to the hospital at the end and says 'did what?' To Harry. Was just amazing. In the book dumbledore was all cautious and timid. I think it worked not reading the books for me. That's my opinion!

I was(still am)about to make that same post. I feel like Christopher Lee or Ian McKellen would have been better than either Michael or Richard, but Ian didn't want the role and Christopher didn't have time.

Well to be fair, Harris didn't read the books either.

According to the trivia for Prisoner of Azkaban, he did not feel the need to read the books. I think this is why he didn't do a good Dumbledore. Plus Richard Harris was the true embodiment of Dumbledore. And Dumbledore doesn't yell