But you're making an assumption that the gospels are objectively correct, whereas scriptures are mostly written from a rather subjective perspective. Also, there are quite a few variations that's found between the gospels, and John's certainly is less like the three synoptics.
One thing to note in John's gospel is that he often refers to "the Jews" in such a manner whereas it's being referred to essentially as an outside group, the importance of that being that even though Jesus and the apostles are all Jewish, by the time you get to the end of the century, they are seeing themselves as being different.
Choosing one Gospel would not make the other Gospels false, by default, though. You would really have to prove that. I think that that is not provable with merely theologic belief, then interpreting them in ones belief system.