Valkyria Chronicles.
The sequel wasn't neccesarily bad per say, in fact they have improved some gameplay aspects such as the enemy A.I., and mission variety.
However, the story and characters in the game were pretty sub-par compared to the first game. The main protaganist is annoying as all hell, and a lot of characters were basically stock characters used in so many games and anime. (Such as Cossete, who is the ditz.)
I also didn't like the new class system in that game. While I do like the increase of variety in soldier classes, I don't like how you're supposed to get them. In order for each and every soldier to upgrade to a higher class, they have to obtain a certain amount of certain items called credits gained by having them participate in certain missions. The worst part is that it's completely random whether or not a soldier gets these credits even if they did participate.
This kind of system forces you to grind certain missions in order for each and every soldier in your squad to obtain the right to get to a different class. Which is exactly what the first game sought out to prevent by making it so that when a soldier class goes up a level, everyone in that class, whether you use them a lot or not goes up a level. This leveling system is still present in the second game, but the credits system ends up contradicting it.
That's pretty much the one major reason why I believe that the game was inferior to it's predecesor. I really hope that if VC3 does come to U.S., they don't use that kind of gameplay system again.