VII is the best game that has been made, XII got so many flaws it's not even funny.
For example the quickenings,summons and music was really bad most of the time, the license system and storyline was too short and the characters had no depth whatsoever and scenes,dialogue between them were not that many..

Vaan is the stupidest main-character i've ever seen in FF game, the only one that really sucked in the end. He wasn't 100% bad but still he kinda sucked. I don't even use him in battle except for stealing.
The only thing i like about this game is the battle system and the side-quests are alright at times.
So it's fun to fight and do missions, the storyline wasn't nearly as bad as Dissidia though, i have played XII over 600 hours, Dissidia under 10 when i stopped playing it months ago.

So comparing it to Dissidia would be alright in my opinion, XII definetly is the better one there, but the worst one in the series along with II.
Although II had a lot better music so yeah