Just because this genre is so rare doesn't mean its that great.
First graphics. While game use sharp hi-res sprites and some nice effects its style doesn't fit my taste because color palette chosen. Everything is in certain redish or yellow like style and aside of very few levels, there is not enough variety in color palette like green and so on. Sure game try to bring something new and its rather dark game with serious story(which I like) but look for example on older fighters we used to play on coin-machines: they were colorful enough yet also with "dirty" feel to describe atmosphere.
Level design. This is weakest point of game. It doesn't success as neither platform neither fighting game when compare to "oldies". Game utilize jumping/climbing/... elements but levels totally lack variety and path branching. For example Claw(also know as Captain Claw) levels offer lot of thinking and ways to reach the end with often possibility to give player to choose if he want to keep up of down path. You can say old fighting games didn't even had this - true but here game fail for another reason: level variety. Every 2-3 levels look just about same but worse, they are just linear path of cloned background. In fact, most levels in whole game look similar for some reason(maybe because limited color palette?). You will pass through endless rooms or roofs that look alike. Again, try to remember fighter games from old coin-machines: city-warehouse-metro_station-metro_train-...... >> and each often varied by other means, also everything pretty colorful yet without loss of serious feel. Every level unique. In Shank, you walk through rather same looking corridor with limited color palette(for the sake of "style") with occasional easy jump sequence without other ways to go.
Enemies. There is not enough variety in my opinion but its ok, worse is that they take rather too many hits. This may give to some feel of slowing you down.
Music is never unique and just uninspired background "wild-west" theme, but it does fit into this game.
Controls. These on one hand make you feel you are controlling more realistic character rather than just simple sprite that instantly respond to any direction, however not everyone may like this in this kind of game. There is certain delay for many moves, for example when using range weapon but also movement a bit and jumping is imprecise which in boss battles may become frustrating. On other hand, on normal difficulty game have very frequent checkpoints and is not so difficult, with bosses mostly wanting you to expose certain movement then use scripted attack. I personally thing controls are ok for this level of difficulty but it may not be for anyone. Platform sequences are not difficult at all however, actually these should be a bit more adrenaline pumping to give any satisfaction.
Bosses. Now this is another minus. Most of them look alike - typical butcher type guy with big belly and SM mask over head. I just felt too many of them were of similar "kind" with different puzzle pattern - which you always figure almost instantly.
Ending was weak, you kill last boss to get your revenge and thats about it. Small cutscene and credits roll. For such dark story premise I expected more to learn. There was "something" you learn during end fight but characters, your life and people you met/fought were never really explained. I understand this is suppose to be old-school fighter but when they did bother to make all this premise, they should have made it to the last piece. Old games at least didn't tried to give you any big story, they rather gave you direct gameplay in nice varied levels. Marianne Krawczyk, author of story - also author of God of War(according to Wikipedia)... don't get me laugh! This kind of cheap "revenge" story without background could even 12y old do better in 10min's! I really loled on this. But to its plus, story was at least serious, mature and well voiced. Also lot of gore, another plus.
So I think game is ok to kill time, but it just cannot reach level of better ones in my book, be it Claw, Metal Slug series or old coin-machine fighters of that era. There is always something of either style this game try to do on mediocre level at best. Narrow levels without any variety and especially INSPIRATION or uniqueness AND with enemies that takes long to kill will just make you want to pass them quickly to see another chunk of story with great cutscene. Only to see cheap ending again.