I didn't know this until the other day from Game Centre CX, but I was under the impression the first Sega console was the Master System. Actually the first Sega home console was the SG 1000, it launched the same month as the Famicom and was decimated in sales, quickly replaced with the Master System. According to wikipedia the most popular game was Flicky, who appears later in Sonic as one of the animals you save.