I prefer the first two Sengokus over the third. The third one completely lost the 80's feel of the first two and it had those annoying frog enemies that took too much time to kill because they were too small.
Whaaa? A different graphic style and a couple frog enemies will sour you on a game with a superior game engine?
Sengoku 3 doesn't have the same "feel", yes, (I will agree that the earlier games had some interesting character design) but the feel it had was great (the graphics are among the best on the Neo) and it also had a fighting system that was far, far more complex and interesting -- it's nearly as complex as a fighting game, in the best possible way -- the controls are much tighter than in the earlier games, too.
Not to mention the great character selection worked a lot better than those transformations ever did.
Gameplay >> presentation, and Sengoku 3 has them both in spades (especially the former).