I got lucky last night and found Fire Emblem Shadow Dragon for $25 @ Gamestop.....it's fun, but not nearly as good as Awakening..
Shadow Dragon ranks as one of the worst games in the series. It's a remake of the first FE game, made over two decades ago. IS added most the mechanics that had been created since the first game, but didn't add any depth to the outdated and now boring chapters, story, or characters. The only good thing that came out of Shadow Dragon was Reclassing, which was used very well in Heroes of Light and Shadow (which was never officially translated and released outside of Japan), and of course Awakening.
If you're looking for depth, check out Blazing Sword(called simply 'Fire Emblem' outside Japan) or Path of Radiance. If you feel like learning about emulation, Genealogy of the Holy War and Thracia 776 are incredible games. Genealogy is where the marriage system originally came from, and it has a much more important role than in Awakening. Pairings matter a hell of a lot more than the child's stat caps and hair color.