X-Men on the Sega Genesis is deep, immersive, and easily one of the best comic-based games ever produced.
This is easily one of the best titles in the entire history of the Sega Genesis, and stands out even today as one of the best comic book based games of all time.
When you begin, you'll notice that you have three settings to choose from. "Amateur", "Hero", and "Superhero". If you intend to beat the game, skip right to Hero, as Amateur has just over half of the levels, and ends with Magneto telling you that an amateur has no chance against him.
After that, you'll notice that you have only four X-Men to choose from. Gambit, Nightcrawler, Wolverine, and Cyclops, each with their own unique abilities and powers. Why they didn't put more characters in, I don't know. But you essentially have four lives, as each X-Man who dies, is dead-dead. They are resurrected when you "reset the system", if you can even do it.
The level design is very deep and rich, the boss battles and various character cameos are satisfying, and the story is just good enough to matter. The gameplay is a hybrid platforming and beat-em-up title that works extremely well. The controls are all smooth and solid, the characters are extremely responsive, and levels get progressively harder, in some cases in great leaps.
All in all, it's a fantastic game that takes you through some of the most memorable settings in the X-Men universe, including The Savage Land, The Shi'ar Empire, Excalibur's Lighthouse, The Future, Mojo's Crunch, and Asteroid M (aka Avalon).
Easily one of the most enjoyable and solid titles of the 16-Bit generation, and highly recommended.