A launch game for the SNES and still one of the best looking games for the system. Super Mario World took the basic ideas behind Super Mario Bros 3 and enhanced them. The over world was now much larger with many more pathways through them. It was a deep game with nearly 92 levels (much of them hidden) making it one of the most robust platformers ever released (a fact that stands to this day)
The biggest change to the Mario franchise that Super Mario World brought was the introduction of Yoshi. Yoshi essentially brought vehicle gameplay to the Mario world. Yoshi changed the gameplay by adding the ability to eat your enemies (some of them even gave Yoshi special abilities). Later Yoshi became popular enough to star in his own games and become a stand alone character (Yoshi was even the central character to Super Mario World 2).
Super Mario 64
One of the simplist additions is also one of the most important. Mario had a little camera man following him where ever he went, and the player could control that camera with the C buttons. The idea of mapping the camera to a seperate set of buttons was a great idea and gave the player the ability to move the camera around to the best position. This is something that has been copied in every single 3D game since (except those with fixed cameras).