Have they generally been benevolent kings, or.....?

Define "benevolent".

Many kings over the centuries, you never really hear about. They didn't do anything particularly good or bad. The famous ones usually did one or the other. Many oversaw the exploitation of other "nations" (i.e. probably not technically nations, but I can't think of a better word) via colonization. I'm not sure that King George was particularly bad (though he didn't appear to be good, either), but had the distinction of being the one the future-USA rebelled against.

In more contemporary times, royalty has generally been a curious anachronism, not doing much at all. The Saudi king is awful (murderous). Queen Liz, and now King Charles, don't have much real power, and just suck(ed) up resources for nothing. I understand some of the European kings (the few that remain) advocate for charity (or maybe it was a princess?).

Overall, I think people actually want kings (for some reason I can't really fathom), but that kings are generally detrimental as they are not required to consider individual rights and liberties.