So I just finished reading the original Sonic comic. While it ends at issue 290, I wanna say the actually story ended in 287 with the defeat of Dark Gaia and the reforming of the planet. The next three issues were just a special arc celebrating the 25th anniversary. I was hoping they would finish off that arc before it got cancelled but they were planning for a fourth issue that never made it. The series ends with Sonic carrying Amy in his arms.
It is kinda sad to think after twenty years its finally over. I read every issue too. It would have kept going if not for that law suit. Shame.