I want to help you OP.... but you may be beyond saving.
1. There are so many unique and inventive levels regardless of whatever tile set is used. Remember that level where you had to jump across dolphins? Or fly through the air avoiding spinning blades? You go into a GHOST SHIP at one point. There are many creative levels, and even the more standard ones have unique secrets and paths. The Special Zone levels alone are completely different from anything we got in the NES games and still stand out as incredibly unique today. They were absurd Mario Maker levels 25 years before that game even came out. The ghost houses and castle stages are among the best of that type even today.
2. Super Mario World has a very unique art design that is completely different from what came before it. From a purely aesthetic standpoint, the world map is far beyond SMB3. It doesn't have the traditional plains/desert/swamp motif that we're all tired of, so going back to the game is still fresh. I love the look of the Vanilla Dome personally. Also the enemy design is excellent and certainly a step above the NES games.
3. It may not have as many levels as SMB3, but they are far meatier and encourage replayability with the Yoshi coins, color block switches, and secret exits. So many SMB3 are incredibly short. Like under a minute. Some SMW levels are quick and straight forward, but others are much more expansive with alternate routes and challenges.
4. The world map doesn't have minigames, true, but I love the design of it, and it serves another purpose: hinting towards the secret exits. It feels like a real world instead of level grids like SMB3.
5. I don't really think it matters what Yoshi is the best, as most of the time you have to deal with what they give you. Obviously for the extremely hard levels you want to have a specific powerup set ready to go, but all Yoshi's are fun to use.
6. The enemies are awesome. Having the GALOOMBAS not die from a single bounce instantly shows you that the game is very different from its predecessors. Chargin' Chucks are awesome and challenging. The koopas are also very fun in that they are multicolored and can still walk around without their shells. They completely changed up old enemies while also putting in fun ones.
7. I never felt the game was super easy. The castles are legitimately challenging, especially that one where you have to ride those snaking blocks. Special Zone will definitely test your reflexes, and many of the secret exits are cleverly hidden.
8. Ghost Houses and fortresses are so different so I don't know how you can compare them. I will say the castle stages in World are better.
World has wonderfully creative level design that was so different from the NES games and still stands out as being very unique today. I like YI but scoff when people compare it to World. I will give you this: NSMBU is an incredible game and probably the best 2D Mario after World. They burned everyone out on the NSMB series, but its swan song was also its masterpiece.