No one is better than Modi in the current context.
Modi like - Amit Shah (only the intelligence part, charisma is missing, won't draw the masses, is always the man behind the scene and extremely competent at that)
Intelligence comparable to Modi - Only Late Shri Arun Jaitley had that kind of intelligence.
A possible replacement for Modi in any contingency is Rajnath Singh. Sure, he lost the LS2009. But he completely redeemed himself in 2014. Rajnath has always been the calm type, and a kisan neta. Beloved of the masses in UP. He has also been the Chief Minister of UP, and Union Minister of very important portfolios as we know. He has met many world leaders. I would like to believe he shares a good rapport with a number of them. Apart from dishing out Kadi Ninda and Muh-tor Jawab kind of statements, he executes those Jawabs with amazing efficiency. What India is today, is not only the credit of Modi. But the result of countless sleepless nights of people like Doval and Rajnath and Shah, who are firmly behind him.
Furthermore, he has strong Sangh backgrounds and is a more centrist leader than Modi. Even the liberals have no complains about Rajnath. His rapport with Congress is good at best and neutral at worst. The only thing that may go against him is his age, he is a bit old. In Indian polity though, that is not at all a big disadvantage. Another factor going for him is that he alongwith Sushma Swaraj, Naqvi, Javdekar were mentored by Lalkrishna Advani. Rajnath is with BJP since his inception. What we might say - Core Saffron!
So if we are facing a situation where a replacement of Modi is required, my vote would be for Rajnath, hands down.