Sing.
Yeah, you're probably right. But more modern works (both in America and Japan) have ninja with supernatural stealth, speed, and jumping ability and sometimes magic powers, something of a monk/sorceror/rogue/fighter. See Naruto, Flame of Recca, or the aforementioned Ninja Burger for an example. Interestingly enough, many of the sources (e.g., Ninja Burger and the new Teenage Mutant Ninja Turtles) have ninja following a code of honor. In Teenage Mutant Ninja Turtles, they explicitly say they follow Bushido! The medieval tales are more accurate, but this way's probably more fun.