For a console to be considered bad to me, first off and the biggest is lack of support from the manufacturer. Whether the system has a few glitches or hiccups, or the intended life span of support for the system. Secondly is developer support. If the system only has developers with titles that I couldn't care less about, its a bad console to me. For others it might not, but for me it is.
My favorite console to this day is the Sega CD. To me it revolutionized gaming with FMV, full audio tracks, and some timeless classics. Yet many consider Sega CD a failure, or a bad console as it was bulky, lack of a huge library that NES, SNES, and Genesis had, and no updated graphical capabilities. However, I still play games on my Sega CD more often than I play my Xbox 360 or Wii.
32X Was a bad console, SoJ pushed it to SoA and said work with it, all the while not telling them they were working on the Saturn. When news of the 32X hit of its release, SoJ was releasing info on its Saturn. This pushed developers away from the 32X. You basically had 1 company playing tug-o-war with itself. SoJ didn't trust SoA, and SoA wanted to do things their way, and honestly if they operated as 2 separate companies they both probably would have succeeded in their own market. But they competed with themselves, killing both systems.