Favorites:
TurboDuo
Sega Master System II (I'll sacrifice a card port and AV out for cosmetics ANY DAY)
NES (Metal Gear, Ultimas, Dragon Warrior, Hydlide, Rescue Embassy, Blades of Steel, lots of ninja games, MM2, f*ck)
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Not favorites, but logged enjoyable hours on:
SNES (more Ultima! more Hudson! & Mario Kart)
3DO (a good selection of computer and arcade ports in the 16-bit era)
XBOX (D&D Heroes)
N64 (Perfect Dark)
SuperGrafx (kind of feels like a distinct little system)
TurboExpress (ditto)