It should graphically, look like this, only instead of just a colorful jpeg background, the world would be really alive. It'd be a more pumped up version of this, utilizing the technology of next-gen consoles.
This is how the game would be:
Title: Sonic World
Platform: Xbox360/Ps3
Rating: E
Story: Eggman has set his empire and is enslaving the inhabitants of Sonic's home! To save it, Sonic must find the seven Chaos Emeralds, spread throughout Sonic's world. In his quest to find them, Sonic must traverse over 40+ levels of speed and action, meeting characters new and old, and forming alliances, (or rivalries!) explore strange lands in your ongoing search for the emeralds, or help the citizens. Get ready to live life through Sonic's shoes!
Worlds:
-Jungle Land
Partner you encounter: Tails
Description: Basic jungle level
boss: Fang
-Metropolis Speedway Zone
Partner you encounter: Amy Rose
Description: Think a world like Chemical Plant from Sonic 2. Some levels have you in underwater areas (you're not in water, rather you're in a floor of a building that's underwater, which you can see through the windows.)
boss: Rouge the Bat
Random Boss Battle!
Eggman: Egg Launcher
Description: Eggman is in a flying tank, shooting missles. Defeat him.
-Volcanic Flame Zone
Partner you encounter: E-102 Gamma
Description: One of Eggman's bases, set in a volcano on a tropical island.
boss: Egg-Robo
-Endless Forest Zone
Partner you Encounter: none
Description: A foggy, haunted forest. Creepy old houses and such.
boss: Shadow
Random Boss Battle!
Description: You are in a pit in a cavern. Eggman is at the bottom, in a machine with spikes protuding form it. Jump from the pillars left to right, to make it to the top, without falling onto Eggman. Kinda like the boss from Labyrinth Zone in Sonic 1.
-Carnival Cat Zone
Description: A carnival island.
Partner you encounter: Cream
boss: Blaze
-Snowy Plain Zone
Partner you encounter: none
Description: A snowy mountainous region
boss: None. Avalanche you must run from.
-Time Tear Zone (tare, not tear)
Partner you Encounter: none
Description: future world.
bosses: Silver & Dark Super Sonic
Random Boss Battle!
Egg-Trial
Description: All of Eggman's classic bots. First it's the Sonic 1 checkered ball, next it's the car from Sonic 2, finally it's the fire spewing one from Sonic 3.
-Echindaopolis
Description: Echinda world from the Tikal visions in SA1
Partner(s) you can encounter: Tikal or Knuckles
boss: Chaos
-Egg Base
Partner you encounter: Tails
Description: Eggman's labs. missions include freeing captives. Later on you must save Amy and stop Eggman from launching his missles across Sonic's world. Classic Sonic VS Giant Robot final boss.
boss: Metal Sonic
It would have the basics mechanics of the Sonic games of yore, only would be a complete reinvention, and introduce a bunch of new things, rather than a simple rehash of a Genesis game.
It'd be more story-oriented than prior Sonic 2D games, and you'd be given choices.
Like Super Mario World, levels would take place on a giant map, and there'd be tons of levels. Now and then, you'll encounter new characters, and be given choices if you want to team-up with them or not, which can either be good or bad (The character in question might work for Eggman, and be scheming behind your back, and later steal your emeralds, lives, and make you go way off-track on the game map.)
New paths and levels open up on the game map if you take on a mission given to you by one of the inhabitants of Sonic's world. (For example: meet an elderly echinda in one level, who's daughter is being held captive, he gives you a map to find her, and a new path opens on the game map, revealing new levels and a new boss. As a reward for saving her, a new option is available in extras mode.
The only real playable character is Sonic, but when teaming-up with a partner, (Partners include Tails, Knuckles, Amy and Cream) you can switch to that character on the fly, with Sonic following. The original characters that you don't know if you should trust or not, are unplayable, and follow. There is still a large amount of Sonic-only levels.
The world would be huge, and there would be towns, jungles, volcanic bases, snowy mountains, labrotories, etc.
Like I said, actual levels would play like the Genesis games, only the way they are set-up on the game map is different, and there is more story.
It would be a long game, and feature a wide variety of villains, in each land, such as Fang, in the jungle world (Bounty hunter for Eggman, who tries to hunt Sonic, and captures citizens Sonic must free. He shows up a lot in levels, ala Knuckles in Sonic 3, causing Sonic problems. He is the main boss once you complete each level in the land. Metal Sonic, (Guard of Eggman's base, who shows up frequently in levels. He is the the boss you'll encounter right before the final showdown with Eggman) Rouge, (A jewel thief in the city land, who is responsible for thefts and is working as an agent for Eggman. She is the main boss of the city land.) and others.
(Egg-robo in Volcanic land, Shadow in Creepy Forest)
There are various 'Tails shops' scattered across the land, which act as a store/warp points, where you can warp to prior lands without spending an hour backtracking, or buy gadgets with the orbs you collect from destroyed robots, such as spring shoes, which make you jump higher, invisiblity shield, which lets you walk through walls, and opens up new paths in levels, or moves such as fire kick, or power gloves, which let you unleash an electric blast on all the enemies onscreen. (all the moves from the Genesis games are standard in levels, as is the lightning orb, the fire orb, and speed shoes. Only original moves/items are avilable in Tails shop.)
Cutscenes would be FMV's, like Sonic Shuffle's.