Microsoft has just unleashed its Xbox Cloud Gaming platform to Xbox Game Pass Ultimate subscribers, allowing you to play titles like Halo and Forza on your iPhone and iPad. It was previously only available to Android users on an invite-only basis.
The Xbox Cloud Gaming service streams games at 1080p at 60 fps, meaning you don't have to rely on your hardware for quality play sessions. And though select games will be offered with touch controls, you'll want to connect a proper Xbox controller via Bluetooth or USB for the best experience. The Backbone ($99 USD) is also a strong play if you prefer a Nintendo Switch-style setup.
Over 100 titles will be available at launch, with more being added on a regular basis. You can sign up here for $1 USD for your first three months, then $14 USD forward.