Happy birthday!
I have really happy memories of getting mine on Christmas day (pretty sure it was 89). What I remember most is the appearance of the console and the size of the controller in my little 7 year old hands. It just looked so cool! I remember thinking, if Batman had a console it would definitely be the Megadrive (the controllers do kind of resemble bats after all, or at least I thought so at the time).
A question for the UK people here: how common where imported Megadrives at the time? I always think of imports as really expensive, but I came from a regular working class family, so I don't think they would have been able to buy it for me if it did cost a lot. Maybe I bugged them enough in the months leading up to Christmas that they thought it was worth the money just to shut me up! I remember there was a small shop in the market where I grew up in East London which had one on display with Revenge of Shinobi plugged in, but no controllers to play it, the bastards! All I could do was watch that awesome opening sequence over and over again.
Mine came in that cool white Japanese box, with the thick gold "16-bit" embossed on the top of the console (not the skinny silver embossing PAL Megadrives got). Most of my games were Japanese imports as well, with their sleek, rounded cartridges and cool box art. The Japanese writing (which I couldn't understand of course) made it all seem very exotic and futuristic to this little London boy. This one in particular will be etched in my brain forever:
Although the MD/Genesis now seems indelibly linked to Sonic and the rivalry with the SNES, early owners of the system will fondly remember that early period (88/89 - 90/91) when 16 bit seemed so next gen and we were blown away by being able to play (almost) arcade quality games at home. Some of my favourite early games:
Revenge of Shinobi - that opening sequence! That music!
Michael Jackson's Moonwalker - I had a friend who could do the moonwalk and thought it was the coolest thing ever
DJ Boy - best fisticuffs beat'em up we had until Streets of Rage came along
Mystic Defender - the little pink babies who melted into even smaller pink babies when attacked really freaked out my little mind!
Golden Axe, Afterburner, Altered Beast - great arcade ports
Ghouls and Ghosts, Forgotten Worlds, Strider - as I understand it, Sega had to port these Capcom games themselves due to the grip Nintendo still had over third parties
Mickey Mouse: Castle of Illusion - I had a "graphics will never get any better than this" moment with this one
Hellfire - brutally hard spaceship shooter
ESWAT - underrated classic
Buster Douglas Boxing - not the greatest game, but the huge detailed boxer sprites were really impressive at the time. Sega swept in to sign Douglas after he beat Tyson, who fronted the famous NES game. Unfortunately, Douglas' career trajectory would match Sega's: causing a shock upset against the then undisputed champion Tyson (Nintendo), only to be knocked out shortly after by a new upstart, Holyfield (Sony).
I think the ages 7-12 are perhaps the sweet spot for max nostalgia in anyone's life, so the Megadrive (and to a lesser extent the Amiga and SNES) will always hold a special place for me.
Looking forward to reading everyone else's memories and experiences of this great console.