Megaman Battle Network 4
The worst sequel of all time. I hate this game. I hate this game with a fiery passion. It ruined a fantastic RPG series.
Super Paper Mario and Paper Mario: Sticker Star
What the HECK, Nintendo?! You come away from The Thousand Year Door, an absolutely brilliant game, and then you release these as its sequels?! Sticker Star was admittedly nowhere near as bad as Super Paper Mario, but its broken and pointless combat dragged down the entire game to a staggering degree. Super Paper Mario was just an unpolished mess all the way around.
Persona 4
Fantastic game, but it's not Persona 3. While a much better game from a technical standpoint, the use of tone and the depth of the story doesn't reach the pinnacle that Persona 3 did.
Rune Factory 4
Fantastic game, but it's not Rune Factory 3. Seriously, this game is really good, but the cast is just not quite as awesome, and there are a few technical decisions that just baffle the mind. Great game, well worth playing, but it's not as good as its near-flawless predecessor.
Fire Emblem: The Sacred Stones
Everyone in the Fire Emblem fan base loved this game. I didn't. It felt to me more like an expansion or a ROM-hack of Rekka No Ken (or Fuin No Tsurugi) than it did its own game. The characters weren't as memorable, the story was "meh", the map and random battle system were implemented horribly, and the new animations just felt incredibly unpolished compared to all the old ones.
Fire Emblem: Shadow Dragon
Of course, compared to THIS game, Sacred Stones is a work of art. Worst game in the series to come to the US. Do not play.
Shining Force III
Only a third of the game came out in the West. Need I say more?
Animal Crossing: New Leaf
Hey, it's Harvest Moon without the farming or any real goal. A ton of freedom, but no real motivation to do anything. I lasted maybe half an hour.
Pokémon Heart Gold and Soul Silver
These are fantastic remakes of the original Gameboy Color games. Pity they decided to junk everything the newer games had improved over the older ones except for the graphics.
Pokémon X and Y
Worst "Important" NPCs in the Series. Period.
The champion is an awful character who contributes NOTHING to the game, the villain is a nonsensical cookie caricature (even for a Pokémon villain).
The plot is not much better, especially coming off the great job they'd done with the last two generations.
Then, to make things even worse, they remove almost all the endgame content that made the game still fun to play for a casual gamer.