I've recently (2008) written a longer retrospective about the Mega Drive for its 20th anniversary, which can be found here.
Years before Sony rammed gaming down the general public's throats with the Playstation, Sega had not inconsiderable success making gaming cool with the Mega Drive (known, strangely, as the Sega Genesis in the States).

The Mega Drive was Sega's highly successful 16-bit games console, concieved in 1987 and released in the following 2 years in Japan, Europe and the United States. A slick, black, 68000-powered box aimed at the hardcore gamer, and promising the power to deliver accurate coin-op conversions. The console played host to many innovations in videogames over its 10 year active lifespan. Although limited to a stark 64 colours on screen, the Megadrive took the prominent video game genres to new heights (and in some cases - such as scrolling shoot-'em-ups - to their logical conclusion). The first and last games commercially developed for the system were platform games. (Alex Kidd and the Enchanted Castle and Vectorman 2)

Megadrive success stories included Sonic The Hedgehog and the John Madden Football series (published by Electronic Arts, who, ironically, Sega had attempted to restrict from releasing 3rd party games for their system). Later games (notably those developed by Traveller's Tales, Treasure, Zyrinx, Clockwork Tortoise and Ancient) achieved technical miracles such as snippets of FMV, first-person 3D, scaling and rotation and liquid smooth animation through the use of composite sprites. The machine never did as well in Japan as in the rest of the world, and few Japanese games were made after 1994.

The MD is still sold in Brazil and several other territories (in the guise of the Genesis 3). Near-perfect emulation on the PC has been achieved, in fact Sega even employed the author of the KGEN emulators (NBA Jam programmer Steve Snake) to port a selection of classic titles to the PC for official re-release. For more information on the machine's history, the family of compatible machines it spawned and its extensive software library, see the Genesis Game Guide (for game titles, try The MegaChart).

Quotes

"What we're talking about here isn't an Amiga without a keyboard, it's more like an arcade machine the size of a portable CD player." - Zero magazine, on first viewing the import Megadrive.

"Spiderman on the Megadrive is more important than any record of the last ten years." - James Dean Bradfield, 1992

"Visualshock! Speedshock! Soundshock! Now the 68000 heart on fire!" (sic) - Alien Soldier, Treasure, 1995

Highlights

Some more recommendations, to complement Leynos's impeccable taste

Shoot 'em ups : Hellfire, Alien Soldier, Contra The Hard Corps, T2 : The Arcade Game, Crying (Bio Hazard Battle), Desert Strike series, Subterrania, Red Zone

Racing : Road Rash 2, Micro Machines 2, Street Racer

Sports : Speedball 2, EA Hockey, John Madden Football ('92 was a good year), FIFA International Soccer, Mutant League Football

Beat 'em ups : Super Street Fighter 2, Eternal Champions (Sega's distinctly average SF 2 clone), Cyborg Justice (arf), Splatterhouse series, Dragon : The Bruce Lee Story

Adventure / RPGs : Phantasy Star series, Landstalker (think isometric Zelda), Sword of Vermillion (pants Yu Suzuki effort), Light Crusader, Story of Thor, Soleil (not at all like Zelda 3, no), Scooby Doo Mystery

Platformers : Tiny Toon Adventures, Earthworm Jim series, Adventures of Batman and Robin, Castlevania The New Generation, Chakan The Forever Man, Magical Flying Hat Turbo Adventure, Vectorman series, Spiderman vs. The Kingpin, Taz Mania

Misc : Devil Crash, Toejam & Earl, Puyo Puyo, Ecco the Dolphin, Mega Bomberman, Star Control

The machine also hosted a truly amazing amount of licensed crap and Amiga ports.