Castlevania II: Belmont's Revenge
If The Castlevania Adventure was an attempt to shrink the Castlevania experience down for the gamer on the go (no matter how successful that attempt may have been), Castlevania II: Belmont's Revenge (commonly referred to as simply Castlevania Adventure II among Western fans, named Dracula Densetsu II in Japan, which translates as "The Legend of Dracula II") was the first time it was actually done well. Commonly derided as too hard, the first Adventure was a flawed game that no one really liked ("system-chuckingly hard" being a common descriptor for it). Adventure II, though, took the few elements the first game managed to parlay properly to the Game Boy and then improved everything else.
Setting the story 15 years after the events of the first game, Christopher Belmont has to go in search of his missing son, Soliel, at four mysterious castles that recently, magically rose from the ground. The player gets to choose where to go, and in what order the castles are handled (a la Mega Man), picking the order and direction of their initial adventure. For series fans, this was a radical new way to start the game (and one that, sadly, was not used again in later titles).
Unlike in the first game, Christopher Belmont actually gets to use the classic sub-weapons. The dagger and axe both make appearances (although in Japan the axe was originally the Holy Cross, a detail that was changed back in later Game Boy Color re-releases of the title in Japan and Europe), and these came in very handy against some of the larger bosses our hero would face. Additionally, unlike in the first game where any hit would reduce the strength of Christopher's whip, only specific attacks (the orbs spit out by one type of demon, Punaguchi) would cause the weapon to downgrade. This makes the game effectively easier and more manageable (greatly reducing the number of portable consoles broken over this adventure).
Not that the game was a cake-walk. Even if the player accessed "Easy Mode" on the password screen, the game still took concentration and skill. Playing through it on "Normal Mode" proved much more difficult -- although not as punishingly so as with the first game. Where the first portable title was created by a group that only had passing understanding of what made the series great, this one seems like it had the care and attention of at least some fans within the company, leading to a game that feels more balanced and fair (like the original title was, in that regard).
The game would prove to be the last official entry in the series for Christopher -- the next Game Boy game starred Sonia Belmont (another under-utilized hero in the series), and Christopher's only other adventure was the "remake" of the first game, Castlevania: The Adventure ReBirth. Although not considered one of the top members of the clan (he didn't get included in the "Greatest Five" in Portrait of Ruin), Christopher had a fitting send off with Castlevania II: Belmont's Revenge, the best Castlevania title on Nintendo's little hand-held.