J2ME Loader is a J2ME (Java Micro Edition) emulator for Android that lets you run tons of apps and games on older smartphones. With this app, you can run most 2D and 3D games, with just a few exceptions.
Like what tends to happen with most emulators, J2ME Loader doesn't come with any ROMs. To play any videogame, you first have to download it (in JAR format) from any other website, but the process isn't hard to figure out. Before running a ROM, you can modify some configuration options.
The videogame catalog that you can enjoy with J2ME Loader is really impressive, including titles like DOOM: RPG, Galaxy on Fire, Gladiator, Heroes of Might and Magic 2, and Need for Speed. The controls, while not perfect, are pretty good too.
J2ME Loader is a really interesting emulator that lets you enjoy a series of games that many younger players probably haven't heard of. It's true that most titles for older mobile devices haven't aged well, but they're still a whole lot of fun, nonetheless.