It's not the only option. Though many people portray it as the best option.
The Moonlight client is an open source implementation of NVIDIA's GameStream protocol. This is the reason why you need a Nvidia account.
Valve is also offering a new way for Steam users to stream their games from a computer. An update for Steam Link, dubbed Steam Link Anywhere, now lets users stream games from their gaming PC to another device over an internet connection.
