The TurboGrafx-16 was the first console to have an optional CD module, allowing the standard benefits of the CD medium such as more storage, cheaper media costs, and redbook audio. The efficient design, backing of many of Japan's major software producers, and the additional CD ROM capabilities gave the PC Engine a very wide variety of software, with several hundred games for both the HuCard and CD formats.
The PC Engine was extremely popular in Japan, beating Nintendo's Famicom in sales soon after its release, with no fewer than twelve console models released from 1987 to 1993. It was capable of up to 482 colors at once in several resolutions, and featured very robust sprite handling abilities. The Hudson-designed chroma encoder delivered a video signal more vibrant and colorful than both the Famicom and the Sega Mega Drive and is largely regarded as the equal to Nintendo's Super Famicom, although that system was not released in Japan until 1990.
Despite the system's success, it started to lose ground to the Super Famicom. NEC made one final effort to resuscitate the system with the release of the Arcade Card expansion, bringing the total amount of RAM up to a then-massive 2048K; a few Arcade Card games were conversions of popular Neo Geo titles. The additional memory even allowed the system to display rendered graphics like those used in the Donkey Kong Country series. The expansion was never released in North America." (Wikipedia)
NEC - PC Engine - TurboGrafx 16 No-Intro 20090529:
Due to broken link the upload has been replaced with the latest set.