The beginning of the Final Fantasy franchise, together in one cartridge, what more can you ask for?
The story isn't the best in either one but what can you expect from a game made in the 80's.
Gameplay in both is typical turn based battles however Final Fantasy II had an innovative leveling up system. Instead of the typical gaining experience and leveling up levels, you gain stats or HP/MP depending on your actions in the battle. If you get attacked, you have a chance for your HP to go up, if you attack someone, you have a chance that your Strength will increase. This was actually a relief from the usual leveling system where you just need to know what level to be to beat a certain boss.
Overall, this game is worth playing even if you played the originals because there are additional dungeons added to each game. Though each game can be beaten in about 10-15 hours each, it's worth it since you get two games for the price of one. If you can find this game in your local store, I recommend picking it up, it's cheap and could get you into a great franchise or let you revisit an old classic.