It is the comparative form of "well off" (compound adjective) which usually refers to money ("well off" = rich) but can be used more metaphorically.
When used to refer to money:
- I am well off.
- My brother is better off.
- Our sister is the most well off of the three of us. (Some people use "best off" instead of "most well off").
As I said, it doesn't have to refer to money. I don't know if Mr Clinton meant that the American population is better off financially than when Obama took office, or perhaps he meant emotionally or in stability terms.
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.