I take no issue with anyone disliking a game. Everyone has their tastes and preferences to what they like and don't like. Personally, I feel FFVII is only sub-par when compared to better games like FFIV and FFVIII. But do I think FFVII was a fail? No way. It just isn't something I personally like.
The same can be said about FFXIII. It wasn't everyone's cup o' tea, but that doesn't mean it was a failure or a bad game. Some people liked it, others didn't. Overall, it received good reviews and was a commercial success.
The problem is people arguing "I didn't like the game. It was a failure. SE has forever besmirched the name of Final Fantasy!"