The best thing in life that our lord has given us is life itself. If we didn't have life we would not be alive we would not have to worry. We were given life as a test to see if we were given all these things for free we would become good people and live in peace and harmony. But we don't we take life for granted we think we have paid for life this is why no one ever stops and thinks am I doing the right thing
Our lord has given us a conscious to decide between wrong and right good and bad. This is the thing which animals don't have. We still do not respect this we still do things which are bad and we do them again and again we do not care or think about what we are doing. If our lord had given the animals a conscious I think and most people do that they would have used it better. None of the people 'look before they leap'. In other words they do not care if the are doing something wrong or write. The actually sometimes don't even know what they are doing.
The second greatest thing is we have been sent on this earth where we can breathe free air. Imagine a place where you had to pay for the air you breathe. Our lord has made the universe. He has put us on a planet and given us so many things and we do not even stop and think about the wounders around us all we do is the same routine. School/work eats sleep. Some people say the do not have time to remember all the things our lord has given us for free. That is not true it only takes seconds and you don't have to use all your body you only have to use your brain is that to hard.
So the best thing in life is life. And all the best things in life are given to us free we don't even have to move a finger. All we have to do is to be good and to think and look before we leap. And also sometimes to stop and think. What is the purpose of life? Why were we sent here? What do we have to do to repay our lord for all that he has given to us?