XII is my personal favorite, since I dislike random encounters, and I love both its combat and its Gambit system, so much in fact that since I played it I find it impossible to go back and replay games like Lost Odyssey, I can't stand them. XII is also probably the most hardcore single player RPG I have ever played. The story is passable and easy, but the optional content is where the true game is. There is an enormous amounts of sidequests to do, and if you complete everything you will be able to unlock some of the longest, hardest and most satisfying boss fights you have ever seen in gaming (one of them took me about 11 hours to beat).
However it does have a lot of problems, most if not all of which are due to the fact that those guys over at Squeenix have seriously mixed up bad game design for challenge. For example, they seem to think that taking away your minimap, normal map and compass in the middle of MASSIVE mazes and having you run around like a chicken for hours before going on the internet to download a fucking map is challenging and not bad game design. They also seem to think that deliberately omitting save points before hard bosses who WILL kill you SEVERAL times before you can beat them and making you reload a save point from 2 hours ago and having to reclear some massive dungeon for another try is not bad game design. And of course, they seem to think that quest logs are not necessary so you usually have no idea where the hell you are supposed to go to complete your optional stuff, and they dare to include quests with descriptions like "Hey, I want you to kill this rare monster, but I don't know where it is. K,see ya!", again totally confusing terrible design for challenge.
Bottom line: You WILL scream and break stuff while playing this game, that is if you want to see the fights that are really worth seeing. But if you are one of those psychotics that starts a game with the mindset "I won't let this game beat me" and repeat this to yourself every, like, 20 minutes, then you will have an absolute blast.