I prefer Super Mario World because it has everything I want to see in a 2D Mario game. In retrospect, some newer installments in the franchise seem like a step back in regards to this SNES masterpiece. Super Mario World boasted an enormous and connected overworld, some of the best castle, fortress, and boss designs in franchise history, and was the first franchise installment where Mario and Yohsi teamed up and still arguably the best.
One of my greatest gripes with the newer 2D Mario games is that the overworld feels loose and disjointed. There is only one world map on the screen at a time. Super Mario World was different. All eight worlds were connected and it was always a pleasure to traverse Dinosaur Land as a connected whole either on foot or using various transportation mechanisms such as Star Road.
The castle and fortress designs were also superb. This was already seen in the castle of the first world with large totems crashing down to smash Mario to pieces. This wasn't only an interesting new gameplay mechanic but also showcased the power of the SNES and highlighted what Nintendo could do with the power of its 16 bit system. The same applied for the spikes introduced in Wendy's Castle as well as the rotating rotor blades throughout. The Koopalings were very well designed and often were grouped in pairs with Larry being a harder version of Iggy, Roy a more difficult Morton, and Wendy a tad harder than Lemmy. The most interesting battles, however, were the unique designs-Ludwig and Bowser. The first was a lot larger than his brothers and sisters but was relatively easy to beat whereas the King of Koopas himself was one of the greatest showdowns in franchise history. Seeing the clown car's eyes turn red with anger after the fourth hit is still one of the most chilling gaming moments I carry with myself to this day.
Yoshi, however, was inarguably the factor that made the game. He was found in four colors: standard green, red, blue, and orange. Each had their own unique abilities such as flying, spitting out fireballs, or causing an earthquake upon jumping. Yoshi may have returned in future games but his potential was never used as wisely. Super Mario World not only introduced the dinosaur denizen to the greatest platformer franchise of all time but also saw him used best.