The question of if Lewis were alive today? Interesting...
What he would think about Christianity as a whole? That's a very large question. I don't really think that Christianity has changed in many ways since Lewis' days. As always in the history of Christianity, the Christians (me not excluded still forget that we are not under law but under grace). I still at times am not patient enough with people I know that are not Christians. I view Lewis as someone that would fight against the legalism of today. This ideal in some circles that Christan rock music is wrong for example. He would emphasis the joy aspect. He would meet people who are searching Christianity out today where they are at. During World War II, he met them in the area of suffering. Today he would not back down from post-modernism. He would say that if his God was not tough enough to survive post-modernism, then he'll go worship post-modernism instead. He would write about post-modernism in his books.