I choose the Sega Genesis. I enjoy the TG16/PCE immensely, but the Genesis was the first console I bought after a few years of playing mostly NES and it captured my time and attention more than any other generation. The leap in graphics and sound were significant and I built some of my fondest gaming memories during that era.
Game series like Sonic the Hedgehog, Toe Jam & Earl, Shining Force, Phantasy Star, Thunder Force, Streets of Rage, Road Rash, Lunar, the Strike games, and some excellent single entries (Castlevania: Bloodlines, Dynamite Headdy, Gunstar Heroes, Strider, Aladdin, Herzog Zwei, Crusader of Centy, Liberty or Death, General Chaos, way too many more to list) kept the Genesis fresh and interesting over the years and I never ran short of great games to play on it. The Genesis library boasts literally hundreds of games that appeal to me. Likely no other console, except the original Playstation, bears this distinction.
Due to its FM chip, the Genesis wasn't a favorite for many when it comes to its sound, but it is for me (I dig the quirky, mechanical, and oftentimes cold and brash sounds of it). When I realized what it takes to coax a particular sound from this type of synth, I began even more to appreciate a lot of my favorite games' soundtracks and effects, as well as the effort put forth in creating them. He's sited a lot, and with good reason, but Yuzo Koshiro was creating sounds on this thing that really stood alone at the time. But even the more simplistic and "vanilla" sounds (by comparison) from other Genesis games still sound great to me and my ears always perk up when I hear a Genesis track or sound effect!
Finally, I love the controller and its evolution over the years. The 6-button Genesis game pad stands side-by-side with the 2nd generation US Saturn 'pad as the two best and most comfortable controllers I've ever used. It's quick, responsive, and I find it works well in all genres, including fighting games (never had any trouble executing 1/4 circle and half circle moves, etc). If I could, I'd use one on every console I own, when appropriate.
I don't discriminate. I own all of the wide-release (and some not so wide-release) US and import consoles from the 80s to the 90s and I play all of them at some point or other. They all have their place and each has games that rank among my favorites, but the Genesis was "it" for me for a long time and has permanently captivated 11-year old me, somewhere in my subconscious.
