I bought Dissidia out of fanboyism, or as I put it: Square-Enix cultism. But I've found I enjoy Dissidia more than I was expecting. Sure the Story mode isn't all that exciting and hell if I can ever get the damn Destiny Point Typhoon summon, but combat is very exciting and challenging. It has a large cast of characters, each with their own set of abilities that keep fights varied. Personally I started with Cloud just because I'm one of those guys.
Combat is fast, movement is fluid, customizing your moves and abilites is a plus. Sure, sometimes a match can end in seconds because Sephiroth's attacks are quick as shit and Break my ass constantly giving him a massive bravery count that could destroy me in one hit....that prick. Definitely have to learn to Dodge or Block if you want to be Pro. This isn't some "smash each other til someone's health is gone" game. It takes some skill and I like that.