Imo, these types of discussions are really First World problem issues. Whatever we choose to believe the source of our excellence (tongue-in-cheek) to
be–random chance, brilliance, God, luck, etc.–most of us have tremendous advantages in life compared to much of the world, and whether we feel thankful/grateful or not for those advantages is simply a personal choice.
In the final analysis, thankful or not, there is a 100% probability that our lives on earth are temporary, so enjoy while you can.