Only problem with this game is it came late in the Genesis era.
The gameplay is what a classic 2D platformer promises. Ristar doesn't exactly jump on enemies to defeat them. Instead, he stretches his arms out in hopes he can grab them and headbutt them! A wacky idea, but it worked! The game also holds secret bonus rounds that are ideal if you wish to get some killer passwords (used to mess around with the game a bit). And the bosses can actually give you a bit of a headache if you don't know what the heck you're doing. And even if you are, a couple of them are still horrifying (Greedy is downright difficult unless you know the pattern during his second phase).
The music is very good, in fact, I loved most of the soundtracks on there! It just added to the game's perfect nature. The one you'll probably like is World 4-1's music, as it changes as you hand the metronomes to the birds blocking the path.
Replay value? Oh yeah, definitely a lot of that! With challenging bosses, hidden bonus areas (some in which are challeging to complete), and with the option of playing the game at a more difficult level (including a secret difficulty), this game has a lot to offer well after you defeat Greedy. And the fact that there's hidden modes where best times in certain runs have been posted...c'mon, don't tell me you haven't thought about beating them. This game truly is a well-thought out game. Outside of Sonic 3D Blast, this is one of the last truly fantastic games Sega has given us on the Genesis. Maybe they were saving such a great game for late in the era, huh? Too bad the 32X killed Sega's popularity, that and the upcoming N64.