Between the Mega CD and 32X, I feel that the 32X was the better idea. However, its timing is what doomed it. It couldn't have been released any sooner than it was, because then everyone would have been up in arms due to the Mega CD being released just recently as well. It couldn't have been released any later (due to said Mega CD only being two years old in the States), because of the Saturn had just launched in Japan (32X launched in Japan about a month after the Saturn), and was (at the time) still a year away in the States.
Such a shame too, as it had more potential than Mega CD, and (on paper) did more with the MegaDrive hardware than the Mega CD.
Maybe I'm just blind with 32X love, but can you imagine if some games had been developed truly taking full advantage of a MegaDrive/Mega CD/32X combo? I bet it could at least match, or come close to Saturn and PSX launch titles.