My hesitant conclusion, made firmer by reading the answers above, is that they are in essence genuine remarks. Though what you quote is an amalgam of three sayings from the same passage assembled together as one quote!
As @Drux noted the source of the quote is clearly Sentiment de Napolon Ier Sur Le Christianisme by M. le Chevalier de Beauterne.
For the fullest English translation of the quotes concerned (that I have found to date) see John Abbot's History of Napoleon Bonaparte (1855), chapter 38 - beginning at the line, "He then saw the two Abbés...".
While Cronin claims the quote is apocryphal, in stating that Beauterne never met Napoleon, he shows that he is not aware of the context of the quote, and appears to have dismissed it out of hand without due diligence. Beauterne's source was never claimed to be either Napoleon or Bertrand, but Montholon (see the book as per link provided by @FelixGoldberg, or the sub-title given by Abbot to his citation from Sentiment de Napoléon sur le Christianisme: conversations religieuses, recueillies à Sainte Hélène par M. le General Comte de Montholon). Thus Cronin's normally weighty opinion seems here not pertinent to authenticity considerations. The quote supplied by @Varrin Swearingen is a further excellent attestation to their authenticity–Montholon clearly stood by them, and Cronin's accusation of fabricating Napoleon quotes ought to have been aimed at him.
I had always wondered how Montholon managed to remember and recall Napoleon's sayings, but I think this expresses the reason for the clear and substantial recall well:
General Montholon, after his return to Europe, said to M. de
Beauterne: “...I have seen it, yes, I have seen it; and I, a man of
camps, who had forgotten my religion—I confess it—who did not practice
it, I at first was astonished; but then I received thoughts and
impressions which still continue with me the subjects of profound
reflection. I have seen the Emperor religious, and I have said to
myself, ‘He died a Christian, in the fear of God.’ I can not forget
that old age is upon me, that I must soon die, and I wish to die like
the Emperor. I do not doubt even that General Bertrand often recalls,
as I do, the religious conversations and the death of the Emperor. The
General, perhaps, may finish his career like his master and his
friend.”
[Reading the John Abbot chapter in full you will note Montholon also kept a journal of his time there, which would further account for the clarity of his recall.]
The sentiments on Christianity, extensive and thorough as they are, demonstrate a learned mind of the very first rank applied with considerable profundity to Christ and his religion, showing him to be thoroughly and deeply convinced, then trying deeply and thoroughly to convince a dear friend, in this case General Bertrand. That such an intense discussion created a lasting impression on Montholon (who was present) can hardly be surprising, Napoleon was after all, a magnetic personality of enormous charisma.
Since Bertrand is portrayed as the key contender against Napoleon in the great discussion that occurred, one would imagine he both could and would have publicly contested such a record if it were not in essence true - as an avowed atheist he certainly had the incentive to do so (he did not die till 1844).
To supplement my answer still further, having just read the French Wikipedia entry for Robert-Augustin Antoine de Beauterne (translated helpfully by Google!), I find these 'sentiments on Christianity' were first published (in essence) in 1837 and according to this French entry:
There was no dispute in the 1830s and 1840s... when many witnesses and protagonists of those years of exile were still alive.
If it is a forgery it is very close to the time, of excellent pedigree, and composed by a superior mind – so I think one might be forgiven for being taken in (as @Varrin Swearingen sources demonstrate, the University of Oxford in 1866 is good company)! His reasoning is generally profound and pretty robust, standing the test of time and placing him as one of the greatest Christian apologists, albeit so briefly and in such a secluded environment.
