Ninja Gaiden Trilogy (忍者龍剣伝 巴, Ninja Ryūkenden Tomoe) is a 1995 SNES collection containing the three Ninja Gaiden games for the NES. It is also included as a bonus unlockable in 2004's Ninja Gaiden for the Xbox.
The three games are straight ports and were not optimized for the SNES, but there are several differences from the NES versions. Passwords are included and the cinematic sequences were redrawn. The third game is based on the Japanese version, with infinite continues and lower damage from enemy attacks.
The ports have no closing credits. Parallax scrolling was removed from the backgrounds of some levels (Ninja Gaiden III stage 2-1 for example). Other graphical changes were made to comply with Nintendo's "Family Friendly" censorship policy at the time (i.e. a pool of blood changed from red to green, and the removal of pentagrams).
Some music tracks are omitted (two pieces of music from Ninja Gaiden III and the stage 1–1 music in the Ninja Gaiden II pursuit cutscenes). A degree of censorship was actually removed from certain parts of the script (for example, Jaquio's "Argh! He's awake" is replaced with "Damn, he's awake.").
Ninja Gaiden Trilogy is a collector's item; in June 2015 Price Charting showed prices for loose copies running anywhere from 100 to 170 US dollars.
Source: Wikipedia