Favorite - Dreamcast.
I honestly think it was all timing for me. I grew up loving the genesis. My first console was the NES. But I found a cool niche and love of gaming on the genesis. The genesis remained one of my favorites over the 32-bit generation. But once the Dreamcast was coming out, I was getting old enough to get a job. It wasn't a legit job since I was around 14. But I worked that summer outisde of town on a farm several days a week. Bought and saved up for a Dreamcast. It is still one of the most nostalgic systems for me.
It might be weird, but I LOVE the sounds it makes. The system has this very distinct calming spin to the disc as well as the grinding of the laser. And although it might be a horrible sound the VMU beep that every dreamcast owner knows makes me so happy.
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Least Favorite - Playstation
It is honestly far from my least favorite but I don't want to put something obvious like the game.com down. And I've never played a 3DO or some others that would probably be worse. I am picking a system based on being a major release and one that I have played.
It really comes down to me disliking the 32-bit generation. As was mentioned earlier it was experimental. And the playstation had the combination of not doing 3D like the N64 or 2D like the Saturn. I also dislike the dual shock. Having said that, it is a good system. Has some FANTASTIC RPGs. It just never really connected with me.