considering the majority of their best series are adventure/platform games, Nintendo. Contra and Castlevania are some of their most important IPs and dying to be reborn, and Nintendo would be perfect to reignite them
I am torn about Silent Hill and Metal gear, maybe Sony would be better with them (although I think Nintendo could do Metal Gear justice)
if I'm correct in memory, Konami has the Hudson Soft properties too right? (Bomberman, Adventure Island, etc.), and those are properties that are perfect for Nintendo.
I think the real key is if the IPs were sold they go to companies big enough to do something with them. I would be fine with them divided between Nintendo and Sony. Microsoft kills things it acquires and I don't know of any third party I particularly trust lately
