Those are rarity ratings from 1 to 10 as described from this site's rarity guide, which was pretty useful and relevant about 10 years ago give or take.
If you play the Sonic Advance games on the GBA, many of the levels are basically press right to win. I've passed at least one whole level just by holding right, and occasionally pressing jump when stuck at a wall or small ledge. There was no real skilled platforming required like in the original Genesis games.
He said many, not most. And I'm pretty sure he said early 90's so we'd be including the SNES which came out here in 1991. Most of the good games that everyone remembers on the Genesis or SNES came out in 1992 or later. So any game pre-1992 would be considered for his statement, and plenty were bad, though several also were good. If you're altering the quote, remove "so" as it's out of context. Many of the games were terrible, that's true, or at least mediocre if terrible is too much. That's still not even saying most of the games. I just disagreed with his specific view on Sonic 1.