9.5/10 for Silver Star and SSSC
7/10 for Legend and Harmony
Silver Star and SSSC had somewhat of a challenge to them, assuming you never power leveled. Legend and Harmony were extremely easy even without and grinding.
Lunar 2 is a better game though. Lunar 1's gets a slight edge to 2 for story, but Lunar 2's gameplay is quite a bit deeper, and its equipment depth is also significantly noticeable.