As one of the most classic arcade shoot 'em up video games from Japan, Raiden series definitely has the most and loyal fans players around the world. To a certain extent, AppNee can put it this way: Raiden is the rare peak work among all flight shooting arcade games.
Ultra Assault is an old, classic Raiden-style 3D flight shooting PC game released in 2003 with multiple high gaming difficulties. AppNee suggests it to Raiden series' fan players, you should not miss it.
Raiden Legacy is indeed an excellent official remake version of the classic arcade game Raiden (雷電) series for PC and Android platforms. It includes Raiden, Raiden Fighters, Raiden Fighters 2 and Raiden Fighters Jet 4 editions in one game, which allows you to fully experience the nostalgia.