G.G. Shinobi: The Silent Fury is what Super Mario Galaxy 2 is to Super Mario Galaxy, it takes a set of widely successful mechanics new and innovative for the series and iterates, refining it into something instantly recognizable but improved.
The original game promoted the idea of synergy, rather than a single protagonist as with previous titles, G.G. Shinobi utilized multiple - each with there own unique ability to progress through a level, yielding bonuses through exploration and ultimately (as the player collects them) coming together to work in unison for the final, most difficult level.
All these mechanics remain in The Silent Fury, with some tweaks. While integrating characters abilities with level design didn't come into effect until the final and lengthiest level of the first, The Silent Fury 2 utilizes this synergy from the start.
As the player collects his companions, previously locked areas, become unlocked allowing both optional, as well as mandatory resource gathering.
In the case of mandatory it comes in the from of multi-colored crystals, one hidden away on each level. For some early levels it is a requirement to replay them, but the Red Ninja's ability (the default character) has his powers sensibly tweaked from earthquake, to a teleport ability in the second game immediately taking the place to the end of the level when done, removing any repetition or redundancy.
The optional elements come in the form of power-ups, health as well as more significantly, permanent health upgrades, buffing characters up for the final run.
Comparative to the first, this is in easier game, the health upgrade can make boss battles a pushover. However, as with the original, as the characters arsenal and experience grows, the final earns it's place as the crescendo, immediately pushing the player to deaths door, becoming an elongated test of skill.
When measured against other titles of the 8 bit period, even the much famed Metroid and Metroid 2- this is a better game. It plays better, it looks better and it sounds better.
If it deserves criticism, many of the assets of the first game, characters, cutscenes and levels are reused - from screenshot comparisons it looks identical to the first game. The graphics themselves as well as the audio, are still very much top of the crop for the system, without question.
Similarity isn't necessarily a bad thing though, Shadow Dancer on it's big brother, The Master System, played very different from the original Shinobi, with completely different graphics, rather than follow a winning formula, it was terrible, the worst in the series.
The Silent Fury along with it's original incarnation are easily the best titles on the Game Gear and for some thee best Shinobi titles. With a focus of exploration over combat as well as synergy over power-ups, these exclusivity built Game Gear titles stood out as something different, giving clear indication as the Game Gears potential as more than a mere mini-Master System.
