Do you think there is a room for centralized coins such as Ripple win over Bitcoin and Ethereum?
If you mean trading volume or capitalization as "win" criterion than it can happen for some period of time. These numbers can be manipulated if manipulator needs to increase them. But I don't think that any coin can take place of Bitcoin as head cryptocurrency in the nearest future(at least). It is primary crypto and it prooved that it is trustworthy.
What is the good part about centralized coins against the decentralized ones ?
The only good part for them is that governments can create centralized coins with their own infrastructure and make these coin(s) accepted everywhere. And as you know it is very important for people to get such assets that is acceptable by majority