Want a lil background? Sure. Sonic the Hedgehog was released in 1991 by the good company who's name begins with S (not Sony... the other one). Made by Sonic Team on Game Gear and Master System (then Mega Drive/Genesis), the game featured a nice marsupial with an odd color, and something that SNES owners envied... SPEED. Noted as the planets fasted hedgehog, the game featured 6 levels, split into 3 "acts", with 6 special stages. Sonic the Hedgehog was an instant hit, and it wasn't too long before Sonic became the official mascot for Sega. Sonic's success was so large, Sega bundled the game with all of their machines at the time (remember those TERRIBLE Pirate TV ads??? Kids, ask your parents about those), and players demanded a sequel. And they got one.

When Sonic 2 was announced, the fans acted like someone turned the adrenaline in their bodies up to INSANE. Sonic 2 was being hyped everywhere. When Sega finally let it be released, they made a simultaneous release on Sonic Twosday (24th November 1992). The game was NOT made by Sonic Team (but programmed by Yuji Naka... programmer of Sonic and stuff), and suffered from being too repetitive. Unlike the first game, it lacked that certain thing that made it special.
However, the game played much like it's predecessor, and with the novel cartoony graphics, did sell quite well. It had the speed, and featured a "sidekick" named "Tails", who some people grew to love... not me though!

The graphics of the 2 games are remarkably different. The screenshot of Sonic 1 above shows the nice, but bland, sprite of Sonic. I prefer this animation, as does Sonic Team, as it was again used in Sonic CD. The detail in Sonic 1 is actually quite good, but is a little sparse at times.
Sonic 2 (the upper right screenshot) featured cartoon-style sprites. Much of the graphic detail was lost, and it seemed that Sonic exists as a flat 2D blue hedgehog (where as Sonic 1 made Sonic have depth).

But 'nuff said about the crummy graphics. How do the 2 games play? Erm. Well. Sonic 1 has the "pick up and play" quality about it, making it easy to get into. Sonic 2 has this also, but to a lesser degree. Once the player has all 7 Chaos emeralds (the grey was not discovered in Sonic 1) in Sonic 2, said player gets Super Sonic, becoming practically invincible. It is a good bonus for completing the (not too) difficult special stages, but it ruins the replay value. Also, "Tails" flying ability is not used her, unless Sonic loses "Tails" when running (I purposely do that).

The music of the two games was done in a similar fashion. The music is suited to the Zones they featured in (e.g. Green Hill and Emerald Hill have jingly porny music), but sound a bit erm... (insert nasty word that I can't mention here). They sound far too like the demos on Casio keyboards (which isn't a good thing, unless your deaf), and are too similar to games released at that time (with the exception of Streets of Rage 2, which was fantastic in the sound department). I usually play with the sound on low, or off completely.

A few short sentences can describe the features of Sonic 1 & 2. They BOTH feature level selects, debug modes (see screenshot of Aquatic Ruin Zone), Slo-Mo, and different endings (well... SLIGHTLY different) if all the Chaos Emeralds are collected.
Sonic 2 does have a 2 player split screen option, which will actually entertain 2 people for a few days. However, when one of the two gets annoyed for losing all the time, it gets tedious and boring.
Sonic 2 also features the super cool "3D" special stage (which some English computer magazines labeled "completely rendered masterpieces"). This is the only reason I still have this game, as they are the only thing Sega seemed to make an effort on. The infamous Spin-Dash was included in Sonic 2, which led on to bigger and brighter things for Sega.

Are sequels any good? Look at Godfather 3...

Sonic 1
Graphics: 7 - Nice touches here. Loses points because of repetition.
Sound: 6 - Not groundbreaking, but it is a cartridge game, so digital sound of awesome quality is not expected.
Originality: 10 - The first Sonic game. Has some new elements that are refreshing.
Lifespan: 8 - After 10 years, I still play this game... 'nuff said?

Sonic 2
Graphics: 6 - Loss of detail due to the cartoon style graphics. The Special Stages saved this score.
Sound: 6 - Still sucks... and I'm not forgiving.
Originality: 7 - It's the sequel to the game that started the series... DUH!
Lifespan: 5 - Play this when you are supposed to be going to church (unless you actually GO to church, in which case take your Nomad and Sonic 1).

Final Percentage - 93% The original by Sonic Team themselves. Thanks lots Sega!

Final Percentage - 89% Much too hyped and got peoples expectations up. Wasn't made by Sonic Team.