A classic side-scrolling platform game.
Rayman is a classic side-scrolling platform game. It's as simple as that. While it's nothing groundbreaking or genre-defining, it really offered a lot more innovation in a genre that was beginning to die at the time of its release. The graphics had imagination, the music was the real deal (not that MIDI crap that most platformers had), the gameplay was unique, and the game itself introduced a new character that inspired a whole franchise of games: Rayman.
Rayman didn't have speed like Sonic, or fireballs like Mario...He had a giant launching fist. There was nothing quite as fun as smacking an enemy in the face from across the level. The graphics, while dated, we're quite brilliant. The detail put into each world was quite amazing and original. The world Band Land, a definite highlight, had more imagination than most games today have. The music was really nothing special, but it was very high-quality and a few tunes we're pretty catchy. At the time, it definitely a nice change from most of the MIDI soundtracks featured in most early 90's games.
Another noteworthy area of the game was the difficulty. Damn, the game was hard! I pulled it back out recently and it's still incredibly difficult. While the games difficulty level isn't really a complaint, as you gather more powers, you have to go back to earlier levels in the game in order to get everything to need to 100% the game. Some levels are so frustrating that, by the time you finish them, you HATE them. You would rather die than go back to them. It's not a big problem if you like a challenge. I would rather have a challenging game, then a game you end up beating in 3 hours.
Overall, Rayman is a great game. While it's not on the level of other classic platformers like Mario, Sonic, Crash Bandicoot, or even the superior Rayman 2, it's definitely a classic for its originality, for starting a franchise, and for, simply, just being a great platform game.