A great fighter for the Genesis!
You have the choice of becoming 9 characters whose lives are cut short by some "evil", events that have caused a being known as the Eternal Champion to freeze time and bring them back so the balance may be even again. A little out there, but I do enjoy the storyline more than most fighting games. The backgrounds of each character are in depth and well written. The "overkills" on each stage are nice if you can pull them off (some harder than others), but I wouldn't go searching them out.
Going into the Contest, you pick one character and that's it, you run with him/her. The difficulty level is steep, but it's more as in the amount of work you potentially have to do. Let's say you win the first three and lose to the fourth. Now you drop back two people to the 2nd fighter you faced, you may be redoing fights over and over again. Also, during your fights, you have this ying-yang symbol next to your life bar. A special move takes a certain amount of it away, if it's gone, you can't use any of them. Though, I hear your opponent doesn't have that same problem.
Once you get to the Eternal Champion, you have two chances of defeating him and his 5 different forms (himself, Shark, Tiger, Dragon, Eagle). You beat them all, you get what happens after your character lives again. You fail both times, you're done, game over, try again, and the EC will tell you why.
One unique feature Eternal Champions has are Training mode. You can have weapons and lasers shoot at you to dodge, you can hit a floating ball all across the room, and I do believe you can fight a hologram of a specific fighter. Another feature is a massive 16 or 32 tournament mode, a bigger version of MK: Trilogy's 8-player battle I suppose. I've never used it, but if you're looking to kill time or really challenge a friend or two, try it out. Finally, the soundtrack is great, starting from the opening screenshot. Each stage, subscreen, training mode has a song that just fits the mood of the game.
So, I think Eternal Champions is overlooked and underappreciated. It holds its own against SF II, MK, and Fatal Fury (probably better than FF). If you love 2D fighters, add it to your collection.