The SNES, IMHO was the best video game console ever. It had all the right cards in place. Name just about any genre available at the time, and SNES had good games in that area. Most all Multi-platform games were just better on the SNES (with the exception of some PC games that ported over horribly). I have to give some credit to Sega for making the SNES what it was, Nintendo had to learn to compete once again, and caused them to ramp up their efforts.
I loved the nintendo/sega rivalry though. The genesis was cool for the reason that it was everything Nintendo was not, and they made it a point to rub it in Nintendo's face. I remember Nintendo's "Play it Loud" ad campaign, and I couldn't help but feel Nintendo just didn't know how to put out a cool image.
Overall, I think Sega would have done better had they not changed things around so much. I think the continual fine tuning they did was a put off to me. There were a few too many system version changes, add-ons, controller changes, even cartridge changes out there. I had one gamepad with 3 buttons, and another with 6. When playing Street Fighter II with somebody, one player was always ended up screwed.

Now the Sega Dreamcast is still something that I still don't understand what went wrong. That system rocked!