Claiming the mantles of both Christian and rationalist probably disturbs rationalists more than it does Christians. I’m okay with that. Rationalists believe that all questions can eventually be answered (although it will probably open up new questions in the process, of course), and that is, fundamentally, the core of their rejection of religion. I believe that the universe will always have some mysteries; specifically origins. That alone is sufficient evidence (leaving aside my personal experiences) in my mind to require a God. Again, leaving aside my own experience, Pascal’s wager and the nature of most world religions implies that there are very few religions that are appropriate to choose. The overwhelming majority of belief systems do not require salvation in itself, merely good behaviors. Only a very few demand some form of redemption for man. At that point, if there is some immortal part to me (and I don’t know that there is, necessarily, much as I like the idea) then it makes sense for me to choose a way that leads to maximal utility.
So, we start with three beliefs, and I think you will see how starting down this path leads to Christianity.
A) The universe has unanswerable questions.
B) God, by His nature, is unknowable in any complete sense. (A topic for a later, MUCH longer post)
C) Only a few religions demand some sort of penance for being human.
There are more aspects to my specific choice for Christ, of course, some of which are much more telling (for me) than these, but they are for another time.