From Sega Retro
The X68000 was a home computer manufactured by Sharp between 1987 and 1993 and only released in Japan. It is a successor to Sharp's previous Japanese-only computer, the X1. At the time, the X68000 was a very powerful system, built from the same or similar components used in arcade machines at the time — the Motorola 68000 CPU, arcade-like video setup (with separate graphics, text, and sprite VRAM), a YM2151/MSM6258 sound setup, etc. — combined with the expandability and space of a computer.
Consequently, many arcade games were ported to the platform, and these ports are generally seen as both the closest to the original arcade versions and, if a game was ported to both this and to the Sega Mega Drive, superior to that version as well. Incidentally, Sega allowed some of its arcade games to be ported to the platform (most were ported by Dempa), and several Mega Drive games, such as Thunder Force II and Granada, were ported from this platform to the Mega Drive.