From what i've read, it seems like the support for the former royal family seems to be very high in Romania. That doesn't have to be the same as a support for a new monarchy but it is a prerequisite if it should ever happen.
I can't see that in any other european country right now. Constantine would certainly love to end his life back on the greek throne but it won't happen. He wasn't very popular when he left tbh and i don't think the greek people would love Pavlos and M-C as their royal couple. They seems to be more interested in living jet set life than to become hard working royals and that's extremly far from the greek culture. Nikolaos would be a better King. But i can't see a restoration of the greek monarchy happening in a foreseeble future. What Greece could do and should do is to stop pretend the monarchy has never existed restore Tatoi, It's surrounding gardens and the royal cemetery to full royal splendour and open it to the public as a museum over the Greek monarchy. That would make a great tourist attraction and younger greeks can learn about their royal history.
The only way Russia would become a monarchy is if Vladimir decides to change his title from President Putin to Tsar Vladimir :-D
I agree that the Romanovs should stay far away.
If there is a country i would LOVE to see as a monarchy again, it won't happen but France has so much of It's royal history and palaces kept that it would be a fantastic constitutional monarchy. But it won't happen. And who should be the King or Emperor ? As the dynasties are fighting with each other now over a throne that doesn't exist and haven't existed for a very long time, how would they do if the throne suddenly did exist ? :-D hahaha. No France is better as a republic !