Is 8GB enough for gaming? Yes.
Is 16GB better? Yes.
8GB has been the standard for gaming PCs for the last few years, with most games rarely using over 6. However, times are changing as always, and so we are seeing more games that benefit from the extra capacity and speed.
There are plenty of YouTube videos and articles that demonstrate a small but still significant performance in some games when going from 8 - 16, and the performance gap will only increase over the next few years.
That said, 8GB is still perfectly viable at the minute, and will run all games with no issues - but if its in your budget, getting 16GB will be better in the long run.