Comparing "Super Mario World" and "Yoshi's Island" is like comparing "Aliens" and "Alien 3," or "Batman Returns" and "Batman Forever." One has almost everything, the other has nothing and just drags the first one down with it. The graphics, music, controlling, enemies, items, and replay value are all noticably better in "Super Mario World" than in "Yoshi's Island." And, for Yoshiboshi, "Yoshi's Story" is better than "Yoshi's Island" (not by much, though).
Vwee-voo! Forget "Yoshiyoshi!" "Vwee-voo!" is better!