If you like X alot, the games you're probably going to like the most are VII-IX.

Those 3 games all have vivid, detailed, beautiful environments that really show off the imagination of the developers, the battle systems are relatively easy to pick up and get into, and the storylines take you on amazing adventures just like X.

I would personally suggest VII, so you can see where the style of X kinda came from. The battles are more fast paced than in VIII and IX, and the story itself is kinda similar to X.

VIII and IX will probably be right up your alley, too. I think you really couldn't go wrong with any of those 3, and taking in how much you loved X, I really couldn't recommend them more to you.