The only time I've ever seen people hate Noel is when they say he is a safe character (and some pairing war stupid shit). To be honest, I agree completely, but it doesn't mean I dislike him. Hell I consider Zack one of the safest characters in FF and it works for him.
XIII you weren't suppose to really like the cast right off the bat, I know I didn't. Even Snow who changes the least, the first thing Vanille says about him is that he seems like he's all talk. Everyone is the worst of their tropes and it's kind of the point. And then by the end they are the best of themselves and it really was a hell of a journey.
But you can do that when you have a cast of 6 (or 9 like other FFs) simply because you have much more characters. You can have someone creepily over perky, or a brat, or an asshole because chances are you are going to like at least one character. And even if you don't, at least one character is going through development and you get to see how all the different characters rebound off each other.
In games like XIII-2 (or Zack in CC), you only get one or two characters you better be damn sure they are likable pretty early on. There's so little else to help buffer the annoying out, and imo the plot isn't so great in either XIII-2 or CC can distract from characters you hate.
The saddest part about the loss is the lack of character development, Serah and Noel is pretty much the same in the beginning and the end of XIII-2. They get sad sometimes but that was less of character development than exploration, and it lasts for about a level.
But then again, the game is kind of non linear, you get all kinds of strange side stories that you can go to whenever you want to. And so Serah and Noel react the exact same way no matter when in the main plot that happens and it makes sense.
You can't do it in XIII, because characters like Lightning and Hope are completely different- and Snow, Vanille, and Sazh have gotten their kind of crippling issues out of the way. Imagine Hope meeting his dad any other time, before he got most of his rage and communications issues out, or after his eidolin when he gets his confidence and his tendency to make speeches. It wouldn't make sense.
So what was I saying? Oh yeah, Noel and Serah are fairly easy and safe characters and it's better for the story of XIII-2. It works for them.
XIII on the other hand, I'm playing again. And I'm enduring hours of grinding to gain the items necessary to buy items and upgrade weapons and accessories.
I like XIII better for the story and characters but XIII-2 is so much more fun to play. And I've played both twice. XIII to get a better grasp on the story (so much easier when you figure out what's going on) and XIII-2 mostly to experiment gameplay wise- I played purposefully underleveled, with different monsters and I switched up my leveling experience to make a mage out of Noel and an attacker out of Serah.