Sonic the Hedgehog 3 & Knuckles is the best of the original Sonic Trilogy. Long, epic, and fun.
Game play: 8.5/10
In terms of difficulty, Sonic 3 is a bit harder than Sonic 2. The Acts are much longer, and every act has a boss this time around. Some of the Acts have retarded parts in them (Carnival Night Act 2 comes to mind) and may take a couple of hours (yes, hours) to get through. There are four-teen Zones in all, unless you play as the other characters.
One of the best features in Sonic 3 is the ability to save data. Now you don't NEED the level select code! The ability to save makes collecting the Chaos Emeralds a WHOLE lot easier. And to add to that, getting to the special stages is SO much more easier to do. You don't even need to collect rings! Just find one of the giant rings in the level and there ya go! If you miss it, don't fret! You have a save file, remember? You can just select which level you want to go to after you beat the final boss. There's also Super Emeralds, but I won't get into that since I need to focus more on the game play, unlike my Sonic 2 review.
Alright, assuming you know how these Sonic games play, there's not much difference to how the basic premise is. You can also play alone as Tails, just like in Sonic 2. But you need to use Debug Mode if you ever want to best the third boss as him. You can also play as Knuckles. And that's pretty much it . . . easy. (Sorry, I'm feeling a little lazy right now.)
Controls: 9/10
Same as Sonic 2, but this time you can fly as Tails, and do other things as Sonic depending on his barrier. Oh, and Knuckles can glide and climb walls. Configured pretty well. :3
Graphics: 10/10
Not as bright, but a lot more detailed. The game looks beautiful, to say the least.
Music: 10/10
Better than Sonic 2. The music in Sonic 3 gives me EARGASMS. God bless the composers of these miraculous tunes.
Overall, this game is the best of the original Sonic Trilogy. There are some stupid areas in a few Acts, but it still holds together as being the best.