It was actually a big success in Japan. NEC America completely botched everything in the US market.

In Japan it came out in 1987, two years before the Sega Genesis. In the US it launched a few weeks after the Genesis. The pack in game was based on an anime that didn't come out in the US.

It's big weakness was probably that putting button batteries on HuCards was awkward, so it didn't really have many longer slower paced games with save systems.