If you need a fix this and don't want to emulate through other means this will do the trick, but the game doesn't play as well as it does on an actual Genesis. Slowdown where slowdown wouldn't occur, even some audio bugs.
Tried a couple unofficial Genesis emulators and they aren't doing it as well as the original system either, very noticeably so. Unofficial Nintendo emulation isn't 100% accurate either but what I use it's 98% - 99% accuracy, you can't notice the quality drop when playing, the only way you'd know is if you were trying some frame-perfect speedrun exploits and the counting was off. I guess there isn't as much interest on the unofficial end to get a Genesis emulator to the same level of quality as exsists with Nintendo emulators. That or unofficial Nintendo emulators have attracted better talent... at the end of the day the only way to get the proper experience from these games is the original consoles on a CRT.
Getting back to this package, it's always ♥♥♥♥♥♥ to pay for emulation that ends up being lackluster, though in this case it's better than what can be had unofficially, so at least you're getting something better for your money, unlike most cases (ie. Chrono Trigger Steam, Final Fantasy V/VI Steam, anything on any of the Nintendo VCs vs. unofficial Nintendo emulation, etc.)
Despite the issues with emulation, the core game is overall a good experience. Sonic has terrible air control, which can be pretty frustrating at times because you can't reflexively twitch away from an obstacle or enemy mid-jump, and for the most part are committed to your route. The sound design, again aside from the emulation issues, is great. Most of the art is high-quality retro grade as well, far better than most indies that attempt to emulate this era, but some of it (mainly in the later stages) seems really dull and slapped together.
The game overall isn't too difficult outside of the bonus stages, where a couple can be more frustrating than fun - it's very hard to end the bonus stages early since you can jump off the sides of walls to avoid hitting the "goals" and exiting instead of getting the Chaos Emeralds. The underwater sections can be annoying when you need an airbubble that isn't spawning and then you die, there is also one section in Star Light (Act 2 or 3, I didn't write it down) where you can get stuck and *need* to take a hit from an enemy (losing all your rings) to get access to a higher platform. The fix of course is to take a different route, but if you're a first time player, you may run into this. It's just bad design.
100 rings gets you an extra life. Unlike Mario games of that era (and most Mario games) where coins would carry over from stage to stage, ring counts don't carry over from stage to stage. They're instead emptied into a score count at the end of each stage at 100 points per ring. This score count means nothing beyond challenging friends to see who can get the highest score. Getting 50 rings to the end of a non-boss stage gives you access to the bonus stage. Clearing all six bonus stages gets you all Chaos Emeralds and the best ending. Getting 50 or more rings in a bonus stage earns you an extra continue. Getting 100 or more rings in a bonus stage gets you an extra life. You get ten chances to collect all six Chaos Emeralds, as there are ten levels that let you access the bonus stages. Acquiring all six Chaos Emeralds gives you a screen letting you know you got all the Chaos Emeralds, as well as a slightly different ending (Robotnik is stomping the words "The End" at the end of the game instead of playing with the Chaos Emeralds). Unlike Sonic 2 and 3, you don't gain access to a Super Sonic mode from having all the Chaos Emeralds.
http://steamcommunity.com/sharedfiles/filedetails/?id=1348164146
http://steamcommunity.com/sharedfiles/filedetails/?id=1348164269
Hitting recommended, but with the caveat of "noticeably not as high quality as the Genesis release, but currently the best way to play this on PC".
There is currently a free official version of this game on Android/iOS. It has a crappy blur filter applied which the Steam paid versions let you remove, along with mod support and other things.
The Android/iOS versions of Sonic 1 and 2 have additional content, some of which was planned to be released in the originals but was cut due to whatever reasons. It also has a higher FoV for widescreen resolutions, which means you see more on the screen at once and it makes the game easier. The game also runs much smoother on the Android/iOS version than it ever has. However due to the forced blur filter I'd still think people would prefer the original Genesis or Steam emulated versions. It would be wonderful to have that version ported to PC with an option to disable the smear filter however.
