At the time of Sonic 1, I saw it, and I thought the color and the parallax scrolling were amazing, but the Genesis was already a household name, at least in the US.
This is my opinion, having been in High School when the Genesis came out.
Sonic 1 was another addition to a great list of titles. Once Sega decided to start bundling it with the Console,rather than Altered Beast, then Sonic was pushed into the mascot role, and people started taking notice what a great game it was.
Was Sonic ever bundled with the Genesis 1, or was it only the Genesis 2 and later? We bought it separately.