Thanks so much for all the responses!
It's just something I'm really interested in, because I can't believe in Him and I wonder how people exposed to the arguments against Him can.
All those responses that say you believe in Him because you can't not believe in Him, I see nothing wrong with that, because you can't choose what you believe.
Personal experience is a fine answer, because I'm just asking why you believe, and if that's why, then, well, you answered the question

It's not satisfactory for helping prove God's existence, but that's not what I was asking, so all good.
Any more responses would also be greatly appreciated (even if they're the same reasons), and again thanks to everyone who has already responded!
I'm struggling with one of your statements: "You can't choose what you believe."
What makes you think that? There is not a day goes by that I do not find myself in situations in which I have to make choices on what I will believe or not believe.
When you're talking about belief in God, four positions are usually taken: He doesn't exist; one can't know if He exists; acknowledgment that He does exist and doing nothing; acknowledgment that He does exist and making an effort to follow Him. The Bible has things to say about each.
First,
the atheist position that He doesn't exist. The Bible says-
Psalms 14
1 The fool has said in his heart,
There is no God.
They are corrupt,
They have done abominable works,
There is none who does good.
Atheists might take exception to the last part of that, but one has to take into consideration that we are all measured against God's holiness-
Is. 64
6 But we are all like an unclean
thing,
And all our righteousnesses
are like filthy rags;
Second,
the agnostic position that one can't know God exists. The Bible says it's clear from what we see around us-
Rom. 1
18 For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who suppress the truth in unrighteousness, 19 because what may be known of God is manifest in them, for God has shown
it to them. 20 For since the creation of the world His invisible
attributes are clearly seen, being understood by the things that are made,
even His eternal power and Godhead, so that they are without excuse, 21 because, although they knew God, they did not glorify
Him as God, nor were thankful, but became futile in their thoughts, and their foolish hearts were darkened.
Certainly though, there are many things in today's world that tend to blind people to the obvious.
Third,
acknowledgment that He does exist. Many people believe God exists but that's as far as they are willing to go with it. In truth, they are no better off than devils and demons, who also acknowledge that God exists-
James 2
19 You believe that there is one God. You do well. Even the demons believeand tremble! 20 But do you want to know, O foolish man, that faith without works is dead?
Fourth,
belief in God and the desire to follow him. In Biblical times, God was more "involved," at least in the lives of the Hebrews. Not that His existence was not made apparent to other peoples; many felt the brunt of His wrath for their evil deeds. But for some reason, He picked the Hebrew nation as the medium through which He would reveal Himself to the world. Yet even the Hebrews had trouble with belief and following God as is evident throughout the OT.
Is. 64
4 For since the beginning of the world
Men have not heard nor perceived by the ear,
Nor has the eye seen any God besides You,
Who acts for the one who waits for Him.
5 You meet him who rejoices and does righteousness,
Who remembers You in Your ways.
You are indeed angry, for we have sinned
In these ways we continue;
And we need to be saved.
6 But we are all like an unclean
thing,
And all our righteousnesses
are like filthy rags;
We all fade as a leaf,
And our iniquities, like the wind,
Have taken us away.
7 And
there is no one who calls on Your name,
Who stirs himself up to take hold of You;
For You have hidden Your face from us,
And have consumed us because of our iniquities.
People heard the word, but they weren't getting the message. So God came in the form of a man, Jesus, to better connect with men and deliver His message of love and salvation, the promise of life for those who follow Him and dire consequences for those who don't. But even though His presence and miracles authenticated His Words, some people still found it hard to believe. Jesus acknowledged this to Thomas, promising a blessing to those, in the ages after His return to heaven, who believe even though they have not seen him personally-
John 20
29 Jesus said to him, Thomas, because you have seen Me, you have believed. Blessed
are those who have not seen and
yet have believed.
Now, even though God doesn't make His presence known as profoundly as He did in Biblical times, He is still at work in the lives of those who follow Him, as Is. 64:4-5 indicates. For those who are willing to read and listen to the message, the Bible is an excellent revelation of God. Those who are "tuned in," see the hand of God at work in many parts of the world even today.
Tune in or tune out. Just like on the radio. See...you can choose.