Jesus says in Matthew 7:

Enter through the narrow gate; for the gate is wide and the road is easy that leads to destruction, and there are many who take it. For the gate is narrow and the road is hard that leads to life, and there are few who find it.

One might question whether he actually meant to assert that few people are saved and many lost, especially since in Luke 13 he is asked the question directly, and appears to refuse to answer:

Jesus went through one town and village after another, teaching as he made his way to Jerusalem. Someone asked him, “Lord, will only a few be saved?” He said to them, “Strive to enter through the narrow door; for many, I tell you, will try to enter and will not be able.”

Nonetheless, the first statement, with the contrast between many and few, looks very much like it says that more are lost than are saved, and even the statement from Luke does not contradict this. Consequently throughout Christian history this has been a common opinion. Thus for example St. Thomas says:

The good that is proportionate to the common state of nature is to be found in the majority; and is wanting in the minority. The good that exceeds the common state of nature is to be found in the minority, and is wanting in the majority. Thus it is clear that the majority of men have a sufficient knowledge for the guidance of life; and those who have not this knowledge are said to be half-witted or foolish; but they who attain to a profound knowledge of things intelligible are a very small minority in respect to the rest. Since their eternal happiness, consisting in the vision of God, exceeds the common state of nature, and especially in so far as this is deprived of grace through the corruption of original sin, those who are saved are in the minority. In this especially, however, appears the mercy of God, that He has chosen some for that salvation, from which very many in accordance with the common course and tendency of nature fall short.

In more recent times some have questioned this idea, or even affirmed the contrary. Thus for example Pope Benedict XVI says in Spe Salvi:

45. This early Jewish idea of an intermediate state includes the view that these souls are not simply in a sort of temporary custody but, as the parable of the rich man illustrates, are already being punished or are experiencing a provisional form of bliss. There is also the idea that this state can involve purification and healing which mature the soul for communion with God. The early Church took up these concepts, and in the Western Church they gradually developed into the doctrine of Purgatory. We do not need to examine here the complex historical paths of this development; it is enough to ask what it actually means. With death, our life-choice becomes definitive—our life stands before the judge. Our choice, which in the course of an entire life takes on a certain shape, can have a variety of forms. There can be people who have totally destroyed their desire for truth and readiness to love, people for whom everything has become a lie, people who have lived for hatred and have suppressed all love within themselves. This is a terrifying thought, but alarming profiles of this type can be seen in certain figures of our own history. In such people all would be beyond remedy and the destruction of good would be irrevocable: this is what we mean by the word Hell. On the other hand there can be people who are utterly pure, completely permeated by God, and thus fully open to their neighbours—people for whom communion with God even now gives direction to their entire being and whose journey towards God only brings to fulfilment what they already are.

46. Yet we know from experience that neither case is normal in human life. For the great majority of people—we may suppose—there remains in the depths of their being an ultimate interior openness to truth, to love, to God. In the concrete choices of life, however, it is covered over by ever new compromises with evil—much filth covers purity, but the thirst for purity remains and it still constantly re-emerges from all that is base and remains present in the soul. What happens to such individuals when they appear before the Judge? Will all the impurity they have amassed through life suddenly cease to matter? What else might occur? Saint Paul, in his First Letter to the Corinthians, gives us an idea of the differing impact of God’s judgement according to each person’s particular circumstances. He does this using images which in some way try to express the invisible, without it being possible for us to conceptualize these images—simply because we can neither see into the world beyond death nor do we have any experience of it. Paul begins by saying that Christian life is built upon a common foundation: Jesus Christ. This foundation endures. If we have stood firm on this foundation and built our life upon it, we know that it cannot be taken away from us even in death. Then Paul continues: “Now if any one builds on the foundation with gold, silver, precious stones, wood, hay, straw—each man’s work will become manifest; for the Day will disclose it, because it will be revealed with fire, and the fire will test what sort of work each one has done. If the work which any man has built on the foundation survives, he will receive a reward. If any man’s work is burned up, he will suffer loss, though he himself will be saved, but only as through fire” (1 Cor 3:12-15). In this text, it is in any case evident that our salvation can take different forms, that some of what is built may be burned down, that in order to be saved we personally have to pass through “fire” so as to become fully open to receiving God and able to take our place at the table of the eternal marriage-feast.

Here, Pope Benedict suggests that the great majority of people go to purgatory and are ultimately saved, although he says “we may suppose,” to indicate that this is speculation rather than a dogmatic statement. Nonetheless there is a fairly large gap between his suggestion and the position of St. Thomas, or the position suggested by Scripture.