I'm going to go ahead and count all of the Big 3's systems as being successful, even stuff like Saturn, N64, Dreamcast if you count it as 90s, etc. I think that the two logical contenders for "most potential" among the rest are TG16, which had a massive library in Japan but did not sell well outside of it, and 3DO which had a lot of big names behind it, western 3rd party support and was definitely noticed by its competitors at the time but once again did not sell well. Ultimately the 3DO's Achilles' heal from the retro perspective is that early CD games just generally are not fun while Turbo seems to have an out-sized presence (bigger than Genesis?) among people I talk to. But boy did 3D0 have a lot of releases- way more than Turbo got in the US- but of a much lower quality.
I noticed some people saying Jag but I think people pretty much got what they were going to get out of that from a consumer perspective. Iffy controller, cartridge based, limited foreign support and a company in financial difficulties did not make for a bright future. I'm not being disparaging here either, out of all these "failed" systems it managed to live up to potential and none of the others did. And of course nobody bothered to even mention the CD-I so far, which had all of the 3DO's negatives (well, I don't think it was quite as expensive) but none of the positives.