Personally i'd say the 32X, CDI and the Atari Jaguar were the most dissapointing consoles/add ons ever made, they just didn't really have any stand out titles
Consoles that aren't dissapointing
3DO - I never expected anything to come from this console when it was 1st announced but by the end it had 30-40 good games many of which could stand up to their peers on the PS1 and Saturn so I couldn't say it was dissapointing, however I'm sure if I'd paid the full $700 when it came out that would've been a different matter.
N64 - I chose the N64 over the PS1 during that gen and felt validated by my decision ever day from then onwards, never once did I feel dissapointed in anyway, the controller was great when you got used to it, the graphics to me looked far superior to those on Saturn/PS1, there were loads of cool 4 player games that me and my friends had great fun with and though the games did cost more many were the best of their genres available for the time.