I recently picked up the RG35XX Retro Handheld Game Console for approx. £50 and the experience has been incredible for the money.
With thousands of retro games pre-loaded and emulators for the GameBoy, SNES, PS1, Game Gear and so many other classic consoles it really does feel strange to be playing almost any game I like from when I was young enough to truly appreciate them.
The controls are excellent, the screen is decent, battery performance is adequate and the flexibility feels unlimited. I have added some ROMs for games that are hard to get and I no longer need to waste my iPhone on a lesser experience.
It is highly addictive and, as usual, I am now looking higher at what else is available. If you are prepared to spend a bit of money you can get a multi-TB system with every game ever released for some platforms, and some even mimic the Playstation 5, and the latest Xbox and Nintendo Switch.
It is amazing how much is out there and how blatantly all sorts of copyright rules are being broken to offer such experiences. And as you may expect, a lot of it is available from Amazon.