Complex sentence: The game was the only "Sonic the Hedgehog" game released for the Sega CD in its lifetime; an enhanced version of the original "Sonic the Hedgehog" and a "Sonic"-themed localization of "Popful Mail" were cancelled.
Split into simpler sentences: The game was the only "Sonic the Hedgehog" game released for the Sega CD in its lifetime. An enhanced version of the original "Sonic the Hedgehog" and a "Sonic"-themed localization of "Popful Mail" were cancelled.