Retro Game Center is a high quality retro emulator that provides a modern, cool-looking, and user friendly interface. It is highly customizable, with adjustable sizes and positions of each button, and enables users to save and load game progress with 4 manual slots and an auto-save slot. 

Additionally, it provides game rewinding so that users can go back a few seconds in the game if they get killed by a bad guy, and features Wi-Fi controller mode for up to 4 players. 

However, it's important to note that this is the lite version of the app which is ad-supported, with some features enabled only when ads are displayed, and no ads will be displayed when a game is running.