A very funny man who had a very long career. There may have been someone somewhere who didn't like seeing or hearing him perform but if so, that person was pretty much alone in that opinion. I first loved his work on his record albums which, contrary to what you might think, were not an accumulation of material by a comic who'd been working for years, writing and testing and perfecting his act before audiences. George Robert Newhart was relatively new to the comedy business and the monologues he recorded for that first record were fairly new. The man just knew, almost instinctively, what an audience would laugh at.
That was why he had all those hit records and all those popular TV shows and some great roles in movies…and why he wasn't unemployed for more than a few hours here and there during that very long career. There are many performers who have one hit situation comedy and then never have another. Bob had another.
There are plenty of obits and tributes online like this one and this one and this one. So I'll just say that I met him a few times and had the pleasure/honor of writing on one of his many situation comedies and that he was just as nice and funny in person as you'd imagine.
And speaking of imagining: I'm kinda seeing Don Rickles waiting for his longtime friend at the Pearly Gates and saying, "Here comes the stammering idiot, late as usual." And Bob with all his deadpan might is saying, "Well, I certainly didn't expect to see you here!"