Is it useful for most people to believe in God?

In the western World I would say the answer to this question is: YES!

In the Eastern World (China, Japan, South Korea etc.) in some places it might be more useful to believe in Buddha however for cultural reasons.

However, it is all a matter of free choice in the end.

Is it easier to stay alive if you believe in God?

It depends upon where you live on earth.

In the U.S. and Europe it is definitely easier to stay alive if you believe in God if staying alive is your goal.

What is your goal?

Without some kind of goal you might not stay alive at all.

So, if you want to stay alive be sure to create some kind of goal and stick with it if you can.

Otherwise, it is very easy to wind up dead before your time.

It's all a choice.

And you make this choice by either choosing or not choosing.

Not choosing is also a choice.

This is important in realizing too.