There are literally hundreds of newspapers sites that could be useful for your genealogy research. Many of them would gladly have you as a paid subscriber. But how do you know which one is worth spending your money on?
No newspaper website has all of the newspapers. There is some overlap between the sites, but their coverage does vary. The best newspaper site for your genealogy is the one that has the newspapers that you need.
Before subscribing to any of the paid newspaper sites, be sure to check out the Ancestor Hunter website. As of August, 2017 there are links to approximately 25,000 free newspaper sites, including the US Canada and other countries. It is definitely well worth checking out!
Good luck with your research.