From its innovation, to its clever use of the Mega CD's technology, to its obscure appeal, Sonic CD is simply superb.
Pros:
+ Save Feature finally!! Allows you to save high scores and your fastest times.
+ Superior, retro, high quality animation movies not only captures the speed of Sonic, but they also help immerse you into the story and its charm.
+ Revolutionary game design adds alot of depth to keep this aging well. The time travel concept is amazingly thought out and carefully implemented to allow players to explore the level designs without getting bored so quickly.
+ Variety in menu screen interface, keeping you from looking at the same boring title screen.
+ Two different endings and time stone collection encourages you to play through the story mode multiple times.
+ Revolutionary Special Stages take advantage of the Mega CD's Mode 7 capabilities, unlike other crappy Mega CD games.
+ Introduces Metal Sonic!!!!!..................and Amy...........lol.
+ Stands out from the other genesis Sonic games due to a different developer within Sega of Japan that handled this game.
Cons:
-- The title screen looks a little too forced. You dont even get to see the ocean much at all in the game, so what's the point of putting an ocean in the background??
-- No Co-op or Multiplayer is kind of dissapointing. This game would have greatly benefited from Co-op.
-- When you play in Time Attack mode, the time travel concept is removed :(
GRAPHICS:
Pros:
+ Sprites look cleaner and there's enemy variety.
+ Backgrounds are extremely beautiful, professionally drawn out to look big and imaginative. Pixels are used to the best availability to not look protrusive or ugly. Backgrounds even scroll, with up to 5-7 different background layers. This effect helps immerse you into this games world.
+ Visual effects are extremely advanced. 3D Special Stages aren't pixelated at all. The Special Stages even utilize more advanced background skyboxes. Effects utilize a pschedelic shine to objects for a nostalgic visual appeal.
+ No framerate issues!! Yay! =D
Cons:
-- None
GAMEPLAY:
Pros:
+ Control is stiffer and much more precise, which hugely benefits from the level design. Jumping from platform to platform no longer requires you to hold back the control stick to prevent yourself from falling.
+ One new move, the Super Peel-Out. This move is used exclusively for this Sonic game. This is very helpful for allowing you to rup up vertical 90 degree slopes and performing speed-runs, which reduces the frustration of surviving a level. It's also better programmed then the spindash. Not only is this new move helpful, but it also has a cute, new animation with Sonic's feet movements.
+ Fun, creative boss battles that don't rape you of your rings.
+ The game mechanics are very simple and adaptable for young ones without cramming a bunch of scripted sequences or annoying puzzles like Sonic 3 & Knux did.
Cons:
-- None..............again =D
SOUND:
Pros:
+ Good sound effects, especially the explosions.
+ There are some cute litte voice clips yelps. Like Amy's cry for help as Metal Sonic captures her. Sonic also has a clip where he says " YES " when he gets an extra life. Like I said, it's cute.
+ 2X the soundtracks = 2X the ear pleasure :)
+ Both sound tracks are diverse and give two types of nostalgic values to the game.
+ The US soundtrack is soothing and stays truer to the modern Sonic games music direction. Not annoying in the slightest and actually stimulates your brain during gameplay without you even realizing it. The theme song, Sonic Boom, kicks ASS!! Nice guitar riffs with classic 90's style female vocals.
+ The Japan Soundtrack is hip, cool, and very, very catchy. This soundtrack reveals the hip early 90's side of the game. None of them are as migraine inducing like some of the other genesis Sonic games are, which is a relief.
+ I think both soundtracks have something for everyone to enjoy =)
Cons:
-- Sonic's jumping sound effect is a bit loud.
-- The Japan Soundtracks theme songs aren't as cool as you'd hope sadly. They sound more like crappy saturday morning cartoon opening themes. Not very suitable for Sonic. The vocalists are another problem. They have very inappropriate tones and actually make the themes sound embarrasingly bad and out of tune.
DESIGN:
Pros:
+ Thanks to the time travel concept, there are over 50 different level designs to explore!!
+ Superior enemy and object placement actually allows you to survive a level without memorizing every single part of a level like the genesis games do.
+ Which brings me to my next point...and I know some fans are going to hate me for saying this, but I'm actually glad Hirokazu Yasuhara wasn't involved with this game. And there's two main reasons. His enemy placement is infuriatingly annoying. I can't count the countless times I've lost all my rings when I try so hard to survive a level even after playing that level countless times trying to make it to the end in one piece without throwing the damn controller on the floor. The other main reason is some of his design ideas. Don't get me wrong, he did establish Sonic's level design philosophy and appeal, but some of his design can be questionable. Bottomless pits, Spikes hanging from every Freakin' corner and wall, and some parts of design that lack flow. Sonic CD, however, combines the perfect amount of leg room, with the perfect amount of navigation exploration, wtih the perfect amount of multiple paths. Levels have the perfect amount of length as well, and don't drag on. You also won't be seeing parts of level designs repeat. Each Act is carefully designed to offer good appeal.
One level your running through an island, the next your in an obscure world with pinball elements, but even with all these pinball elements, you still get the perfect amount of leg room. The next level your navigating a bright, colorful labyrinth of water, the next you're litterally bouncing 80 feet in the air after touching a gravity altering ground as you land on rotating platforms allowing you to use your brain to make each careful decision without falling in a bottomless pit. The next level, you're running through conveyor belts, the next you're running through a beautiful highway in the stars as you speed through long stretches of pipes, the next level you're in a race for your life with Metal Sonic!!!!!! Oh yeah !! =D Then you finally get to Eggman's base.
+ Lots of obscure design art and objects prevent the levels from looking bland without disorientating you.
+ Special Stages are great, fun, challenging in design, and very clever.
And there you have it, Sonic CD is quite simply superb, and all of its variety and concepts have allowed it to age well.