Regarding the first film I'm the infamous "not as good as the book" type of critic.
So when I see some sort of water elemental of sorts in the trailer for this film and can't think of what that corresponds to in the book I immediately decide I'm not bothering to waste my money on this one.
The first one seemed to try way too hard to be Lord of the Rings. Now I'm sure there's a fair share of Tolkien fans that felt that the Lord of the Rings films weren't Lord of the Rings as well. But they tried really hard to make it a big epic battle movie and that really didn't fit the feel of the book to me.
I think part of the problem is that LotR has made the big fantasy themed battle a cliche. You look at this and 300 and the Golden Compass and Beowulf and they all seem like they're trying to be like LotR. Hell even Harry Potter's trailers try to make it sound a little more LotR than the resuling movies are. It's the typical Hollywood cookie cutter. Like LotR, The Chronicle of Narnia are a popular fantasy series and obviously they want it to be their LotR. But it isn't. It doesn't quite fit. For me it doesn't help that I find those types of battles rather dull now.
The worst offenders for me in the first film are the new fox character (or maybe he was a wolf; I can't remember) and the DRAMATIC ice flow scene. Since The Lion, the Witch, and the Wardrobe was actually written by someone with, you know, talent these hackneyed scenes stuck out like a sore thumb. But then any time Peter Jackson decided to get cute with his LotR films you got dumb sh!t like Aragorn falling off a cliff, landing in about three feet of water, and not only surviving but suffering no injuries. So it's kind of a problem in general when someone else decides to add their own idea into a literay classic. LotR still worked though. The first Narnia doesn't do it for me even when it's following the source material.
To be fair though Prince Caspian isn't as good of a book as The Lion, the Witch and the Wardrobe. So if this film isn't as "good" that's somewhat expected.