It was the same for me. I first was introduced to the franchise through the SNES version. The Genesis version seemed rarer, compared to it's SNES counterpart, but it's so much more fun to play.
The SNES version ramps up the difficulty for no apparent reason. The worst change is probably to enemy defense. If Adol doesn't have the right weapon in any version, the enemies will take reduced damage and you'll hear a special sound indicating your attacks aren't powerful enough. In the SNES version, however, that damage reduction has been bumped up massively, with enemies that take up to 90% less damage. Excessive level and money grinding basically becomes mandatory, as does gratuitous use of the Power Ring. Speaking of the Power Ring, the rate at which lose Ring Power in the SNES version is twice as fast. I'm not certain if this is a bug, or if it's intentional, but either way it makes the game a lot harder.
The enemies in the SNES version are just wonky in general too. Hit detection is off compared to other versions (try dodging Dulan's swords in the SNES version), and many of the enemies move faster for no apparent reason.
It's a real shame. The other versions are fantastic (if difficult) ARPGs. :\
