Nintendo (Advance) Wars. Getting WarGroove recently was nice, but it still doesn't compare to Nintendo's polished tactical turn-based strategy series.
Golden Sun also really dropped off after the first two, fantastic, games. I felt mixed about Dark Dawn when I played it, but it was still better than the series just dying off completely.
The reason for both of these games not receiving sequels in a while is mainly that Intelligent Systems is focused on Fire Emblem (also great!) and Camelot keeps making Mario sports games. (Was mostly good on the GBC.)