This is easily in my top 10 games of all time. Skitchin uses the engine of Road Rash (or vice versa, I forget which way it works), and the basis of the game is also similar to Road Rash, but much much funner. The idea is to race to the end of a level, performing tricks, riding the back of vehicles and smashing other skitchers in the face with baseball bats. While the graphics may seem dated, I absolutely adore the music. Which, if I recall correctly, was actually recorded from real instruments and somehow translated onto the Mega Drive for proper 90's tunage effect.
I hope I don't need to explain the premise of Bomberman to anyone in any great depth, so I'll point out why Mega is so great. I love the joeys, which, to my knowledge is the only other game bar Saturn to feature a ride-on animal with powers (I think the racing games had them, but they don't count :P ). I love the level design, which is so simple and atmospheric; snow levels and lava levels do their jobs so well, with their own area-specific quirks and features. Such a great Bomberman game, and my second favourite after Saturn. It's so cute and funny too.
James Pond 3
"We are depending on you, Pond!"
This is a total dick of a game, but still brilliant. Quite different to the first two JP games, it's a platformer with what feels like an endless list of levels. You're a secret agent fish trying to foil a secret plot to steal cheese from Mars with your frog sidekick...or something along those lines. What's not to love?! Using an array of items (haunted TV, anyone?), you find teacups to progress though levels, find secret areas, kill mice, and so on.
Another dick of a game, but superb nonetheless. Puggsy is, I believe, one of the first games to really utilise physics in its gameplay. While on the surface, a simple platformer, Puggsy is in fact laced with often complex puzzles and item combinations. Items can be stacked to reach new areas, or used to bounce and climb environments.
Mega Lo Mania/Tyrants - Fight Though Time
Ok, not exactly a Mega Drive exclusive, but its still a favourite of mine. A simple but effective strategy game where you play a god guiding your peeps though eras of time, right from cave men up to nuclear level.
Micro Machines 1, 2, and 96
Too difficult to pick a single one, so all of them. Top-view racer, as you probably all know, with different vehicles depending on the tracks. Levels got damn hard as it went on.
Side scrolling shooter of AWESOMENESS. Not sure how to describe it any further, you really just need to play it.
Surprisingly great film-game adaptation. Not very true to the film of course, but who cares. A very different concept to any other game I've played, you basically booby trap houses, take items from said houses and construct guns and other weaponry which you then use to fend off the two robbers. Great fun. Apparently the SNES version is completely different and total arse.
AKA: Iraq: The Game. :P It does have some chilling similarities you must admit. Again, not an exclusive title, but whatevs. You're a US (I think?) chopper killin' bad dudes in the middle east, and blowing up a hell of a lot of shit in the process.
The Lion King
Difficult to pick a final game, I was torn between a lot, but this just won out. Another non-exclusive, and one of the great 90's Disney games, you are of course Simba, platforming your way to becoming king of pride rock, while ragequitting at the stampede level in the process. Some great 16 bit Elton John tunes in there. :P
Honourable mentions to Theme Park, Golden Axes, Streets of Rage...es, Mortal Kombat 1+2, Spiderman v Kingpin, Jurassic Park and Beavis and Butthead.