Well, it certainly should be ahead of systems like the Saturn and Turbografx/PC Engine CD... certainly destroys the US Turbo/PCE CD, that sold like maybe 100,000 total (CD+Duo combined). Saturn only sold 9.5 million worldwide, maybe 2 million in the US total, so its sales were slow too. On that note, Sega went from 20-something million Genesises in the US, to 2 million Saturns. You can have a massive collapse.
You also see that in Atari, going from the 7800 (which actually sold okay) to the disappointing Lynx and very badly selling Jaguar. And as for the 3DO and Jaguar, the 3DO sold a couple million max worldwide, while the Jaguar sold 250,000 total, about half of those on clearance after it was discontinued. The Jaguar CD probably sold only one shipment of 20,000.
For a more positive situation though, it took a couple of years before the Genesis started selling well. Sure, in 1989-1990 in the US the Genesis beat the other new system, the TG16 (even though the TG16 had better games), no question, but its sales weren't great, not until Sonic in 1991 (EA Sports was 1991 too, but Sonic was the initial hit of course.).
However, every generation, of course, has sold more total systems than the one before, so just comparing raw numbers isn't entirely helpful, because of how that leaves out that the market is larger now than it was then.
