Genesis/Megadrive easily.
Never had a Saturn, but I've looked through its library of games many times, and there are still only a scant few gems that really catch my attention. And the Dreamcast is great, and has a few of the greatest exclusives ever, but I think the system gets built-up a little too much by "cult" gamers these days as some kind of golden shining moment in gaming history, going on about some kind of nonexistent "cohesion" between the various Sega-made games in its library and whatnot. But at the end of the day, I just see it as another gaming console with only a small few games that truly appeal to me. Granted, some of those games are among the greatest ever made, but the amount of them is far too small for me to give much credit to the DC itself.
The Genesis is pure gold, though. The original Sonic games are near perfection, and the system is home to a huge host of brilliantly fun titles.
Rocket Knight Adventures, Ranger X, Shining Force, Wings of Wor, Comix Zone, Gunstar Heroes, Flashback, Shinobi III, Bonanza Brothers, Target Earth, Landstalker, Phantasy Star series, Alisia Dragoon, Beyond Oasis, Rolling Thunder series, Uncharted Waters and New Horizons... the list goes on and on.
So many games with so few negative points to them.
More than almost any other era of gaming, the 16-bit era was all about good, simple fun . And the Genesis/MD was absolutely exemplary of that.