No, it is certainly not psychotic - but I think it is delusional.
It might be rational if one has already accepted the evidence as to the validity of a particular religious belief (that which makes sense to oneself), but when this is stacked up against so many other similar but different beliefs perhaps it is not that rational. Although with so many of these religious beliefs having some kind of belief in an afterlife it perhaps is more rational than irrational, but numbers believing are not that important as to such being more likely. The numbers having a particular religion are probably more the dice of history rolling than much else, such as superiority.
For many of us no doubt there is an issue as to such beliefs affecting one's life (and others) - as to how one might treat others or in expectations as to this life and/or as to any future life. Without such beliefs, many will try to live this life (the one and only) such that the consequences of such are important for oneself and others, without relying on some future justice or enticements. So perhaps trying to make this world better for all and not just for themselves. Also, given that suicide is very common, many might be doing such in an expectation of some better future life or as to exiting an existing painful one. If there is no such afterlife then only the latter is actually valid.