I don’t have any good examples that I know of, but I am very curious. To me though, a rivalry is a rivalry when two or more of people are closely competitive. But is it really a rivalry anymore when someone has more victories over the other? I don’t think so.
This doesn’t feel like an answer to the question. Sounds like you’re saying that Android and iOS are both now similar, not that one has been victorious over the other.
I would say it is one sided in that the user gets the same treatment/experience from either platform even though they are consider rivals and each company would argue they are different.