Yes, the MSX had a "Cart-only" system. It was developed by Zemina. I don't remember its name, but I remember it came in either Blue or Pink colors.
Zemina was famous for its bootlegs copies. Many people had 1942 copies that were "Copyrighted by Zemina", while the game was actually made by Ascii. The same happened with Project A 2, and a few others. They also made some games by themselves, named "Bubble Bobble", a version of Bubble Bobble for the MSX 1. It's horrible. They also made "Bros Adventure", a copy of Mario Bros, Super Boy II, a copy of Super Mario Bros, this one is pretty good actualy, and Super Boy III, which is a copy of SUPER MARIO WORLD (Yes, the SNES game), and it's also pretty good. Don't ask me where is Super Boy I though
Yes, Zemina only ripped people off. How they did manage to make their own system is a mystery
But, going into the topic.
It's funny, I have never considered myself a "Sega fanboy". I think they made some of the greatest arcade games ever, but I am no big fan of them. When I was thinking about what I should vote, the doubt was exactly between their 3 main consoles: Mega-Drive, Saturn or Dreamcast, for all reasons that have been stated here already.
Sorry, the SNES can't compete with the Mega-Drive. It may have more colors and the Mode7 chip and all, but the Mega-Drive library is much better. And the Mega-Drive also got a very good Sensible Soccer port, better than the SNES one
The Mega-Drive had all the Treasure stuff (Now, I AM a Treasure Fanboy. They are awseome!), M.U.S.H.A. the Thunder Force series, Castlevania Bloodlines, Contra Hard Corps (Both are better than any Snes counterpart), Sonic games, Streets of Rage 1,2 &3, The better version of NBA Jam and all MK games. Super Street Fighter 2 was also slight better on the Mega-Drive, and the 6 button joypad was much more confortable to play it than the SNES one (Alas.. this joypad is the BEST EVER MADE, period), Truxton, a better port of Raiden, Ranger-X, Moonwalker, Global Gladiators, Puyo Puyo 2, Shinobi games, Road Rash, Desert Stike (Much better than the horrible SNES version, not as good as the Miggy one
), NHL games are much faster on Mega-Drive, as are the Fifa games.
The SNES can't match this.