He was elevated to CEO of Google to keep things running as-is while the founders moved their exciting ventures up to Alphabet. When those other bets were abandoned, Sundar was left as the top engaged executive, but he's still only a caretaker when the company needs an actual leader with vision to navigate their competition.
So, no. He has not been a good CEO. He was a good middle-manager and a decent CEO at best, but he's not been what the company needed, and he's definitely not what they need today.
He's lucky because the entire market has increased, but that's his doing. He could be replaced by any overly cautious algorithm and the results would have been the same.
What is interesting though, according to Wikipedia, is that he is not a software engineer nor a computer scientist by training. He is a materials scientist with an MBA and apparently briefly worked at McKinsey.
Does this limit his tech vision? Hard to say.
Satya Nadella however has a Master's in Computer Science + an MBA comparatively.
If you're saying that Android and iPhone/iOS are very similar, that seems like a good thing?