Tips to make XIII Enjoyable:
Turn off auto-attack
Ignore the story
Rush to post game.
Alright, what happens post game is that the game opens up considerably. More battles, that require some actual strategy to it, item hunting, optional areas, repeatable battles so that you can try to get better at them, and more overall customization. The crippling linearity is gone once the credits roll, and a lot of the battles become far more enjoyable.
If you remove the auto-attack, the game swiftly becomes about quick thinking, ad accurate menu navigation. The paradigms system actually Adds to the combat to make it more frantic, and takes more careful planning. In the last stages of the game, a paradigm swap to the wrong thing for too long could spell out doom for the party. However, after getting everyone's Crystarium maxed out, the best paradigm palette, is simply Paradigm x3 for each of the six roles.
No, the game is not great, it's merely passable, but it is far better than people make it out to be.
Now then. XIII-2. XIII-2 is far better than the prior game. It's a lot less linear, there's tons of things to do, hard battles (Until you get to a certain power level, then everything falls) The qualms I have with it, mostly lie in the leveling system. The leveling system does allow you to end up with significantly less than optimal characters. The monster raising aspect fits well, and actually lead to much better paradigm diversity (as each monster had a role, and you can only have three on your party, which means that though you can set up 6 paradigms, only three roles are available for the monster portion of your party at any given time) The ability to "tune" paradigms is a nice addition too, as it allows you to set whether the party targets individual enemies, or if they target the same one. The music is XIII-2 is kinda awesome, the things to do are so much better.
The plot is still garbage. Toss it out.