Any idea? They showed up at the church but it didn't mean they were religious deep inside.

Good question, even though I think this has been discussed before. Well, of course when you consider that Vito and Michael were first rank criminals you definitely cannot tell they were religious men, at least in the deepest meaning of the word. That being said, they certainly paid formal tribute to the Church, especially in rites and ceremonies, a formal hommage that is (still today) not uncommon at all in Catholic mobsters. Mind you, this attitude does not mean to be religious inside, because if one believes in God and in his precepts he certainly doesn't kill people or get people killed! It's rather a way to strenghten one's power being close to a most honored and respected institution like the Roman Catholic Church.
However, I like to think that ageing Michael realized the entity of his sins and repented, as we understand from his discussion/confession to Cardinal Lamberti in one of the most meaningful and touching scenes of GFIII. When Michael confesses his crimes, especially the killing of his own brother Fredo, and cries, well, he might be listening to God's voice. But since nobody goes to Heaven without tears in his eyes, Michael was going to suffer the most terrible punishment for his sins, the death of his beloved daughter, Mary, who was to be killed instead of him. From a religious point of view, this is a very powerful story of perdition and redemption. The most atrocious sorrow a men can suffer - the death of his own child - is Michael's own Cross. It is possible that Michael, dying alone in his armchair, at the only presence of a dog, in a Sicilian sleepy summer scenario, while crickets were singing aloud, asked for God's forgiveness. And got it.

Even Hitler used to refer to God. Religious is as religious does. Of course, Michael never murdered anyone on Sunday.

What day of the week did he whack Carlo and rival mob bosses who got in his way?

Neither was religious. We never saw Vito in a church, either in the film or the novel. The novel says that his wife went to church every day to pray "that his soul don't go down there..." In the novel's description of the Dons' meeting, Puzo says that the West Coast Dons' bodyguards knew karate, which the other Dons regarded with as much bemusement as "amulets blessed by the Pope, though it must be said that some of these men were religious, and believed in God." I inferred that Vito wasn't one of them.
In the novel, Michael wanted his kids to be raised as Protestants because it was "more American," and was disappointed when Kay, instead, took instruction in the Catholic church so she, too, could pray for Michael's soul. True, in GFIII, Michael did make his confession. But I took a cue from Cardinal Lamberto, who, even after he forgave Michael, said: "Even now your life could be redeemed. I know you don't believe this." [emphasis added].

Is'nt it just as with real life mobsters...they are bought up in religious communities/neighbourhoods?
The religion is always in their lives..it is just something that they can switch off & put to one side whenever they need to!
Many mobsters wear crucifixes round their necks but i wonder how many of them get to Confession regularly?
I think Vito & Michael were the same..religion was just something that was in their lives...
You don't have to be religious to go to Church do you?

Excellent question RVA, I have thought about it several times. We do not have much info about Vito's religious beliefs. As far as michael is concerned, we have mixed messages from GF1 and GF3. In GF1, we see him answering "I do" for all the questions the priest asks like "Do you believe in God" , "Do you renounce satan" etc. But at the same time he is killing the heads of 5 families and also Carlo. This makes me feel that he attended church because of tradition, rather than for religion. But in GF3,after he confesses to the priest, he says to Connie "It was the man. A good man. A true priest. He changed things." Notice he says "true priest". Remember michael is the person who has scant respect for senators, governors etc because they are part of the same hypocrisy. Maybe michael had turned religious by the timeline of GF3.

I would like to know what JM thinks about this question.

I am not JM, but here is my take.

Both are culturally Roman Catholics, and certainly Vito would never go outside of the Church to say, marry off his daughter. The whole notion of "Godfather" is related to standing witness to a baby during Baptism, so socially they are inextricably tied to the Catholic Church. That said, I don't think Vito was a believer. During the peace conference among the Dons in New York, COrleone makes a comment about how gambling, even women" are forbidden by "the pezza novante and the Church." So I think he sees the Church as an institution aligned against him but one with which he muct deal.

Michael is less religious in his younger life, but if GF III is to be believed, he does seek redemption through the Church. Of course it is too little too late.

WOW, your takes are music for my ears, DT!

PS. I feel flirtatious today.

I think we're makig too much of this. Some people are not religious really. They believe in God, but only in a cursory way. But God and his commandments doesn't affect their behavior. Vito couldn't help but grow up religiously. I assume the same about his kids. But there's no evidence in the novel or movies that religion was anything more than a backdrop to their lives. Yes, the church was an institution that Vito had to acknowledge and account for.

Also, Michael went to see Cardinal Lamberto for resolution of his problems with Lucchese et al not for absolution. That was a happenstance.

As long as we know him, Michael would have never opened his heart if he wasn't in true need of being listened by a religious authority and possibly of an absolution (we know he thought he could not be forgiven for his sins, but that doesn't mean he did not want to). It's true he did not go to Cardinal Lamberto for immediate religious reasons, but their conversation soon turned in something more than business, much more. We don't see Michael in tears often in the trilogy. In fact I doubt he ever cried elsewhere. This time he cries and scream his sins out. This is not a happenstance IMO. This is a man (better, a soul) who is at a turning point of his life. Now, I don't think he became a saint in the last years of his life, but I like to imagine that he spent those years in search of redemption, especially after Mary's death. And if he really repented for his sins and sincerely asked for God's forgiveness, he no doubt got it. That would probably be the only "deal" he could not manipulate on.

I think when it comes to the Vito, Michael, and the Catholic Church, the men looked to the church as more of a business or institution. Something to benefit from members practicing good policies, as it is designed.

The pope tells him its never too late to confess your sins, no matter how deep they are.

thats not a quote either, im terrible with quoting