The megadrive was my first ever console (spectrum up until then), though I had played on friends master systems before, but christmas day, firing up sonic and altered beast, is probably the single greatest memory of my childhood.
I played sf2 and mario kart on the snes more than any other game before or after and along with a handful of other essential snes games these pretty much held me through my early teen years.
After that I went on to the playstation, which I loved, but the magic of those early 16 bit years never came back to me after that.
In terms of which system I like the best, all I can say is I sold my megadrive and all the games (for almost nothing), but I never sold my snes.
In terms of which was actually the best, I really don't know, I haven't played nearly enough of the games to a significant depth to be able to say, but I can say that the snes controllers were better imo. Also, the snes just felt a bit more polished in many ways, it was kind of like mcdonalds versus burger king, when a BK burger is right it's perfect, but you're more likely to walk into a BK bathroom and find a name written in shit on the wall.
Edit: actually, in terms of a polished product, I preferred the megadrive boxes, plus I loved the manuals with the proper solid spines. Hated those big gay EA carts though with the yellow plastic tab.
On either count, I think this is incorrect. The SEGA games were top notch, but the Genesis library is big and quality and a lot of that is because of the third party titles. 
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