Sony announced it’s soon-to-be best-selling console of all time in March of 1999, and on September 20, 1999, at the Tokyo Game Show, fully showed what the system would be capable of. The North American launch for the system on Septemwas vastly better, with more systems and launch titles available, but still faced its own problems from Sony and the PlayStation 2. Just a quick side note here, it still blows my mind that Ocarina of Time, one of gaming’s most impressive titles at the time in both graphics and gameplay, only came out one month before the visually stunning Sonic Adventure! By the end of the fiscal year, things sadly didn’t look much better for the Dreamcast with sales only hovering around ~900,000 instead of the 1 million mark Sega had hoped for. Thankfully one heavy-hitting title, Sonic Adventure, would come within a month of launch on December 23, 1998. The 4 launch titles for the system's launch ( Godzilla Generations, July, Pen Pen TriIcelon, Virtua Fighter 3tb) were also considered to be lacking.
Contrast this to the N64, which had managed to ship ~700,000 units within the same time frame. The Dreamcast only managed to shift ~140,000 units in its first few days.
Shortages in manufacturing the systems PowerVR chipset drastically cut the expected stock of systems to be available at launch. First was the lackluster Japanese launch of the system on November 27, 1998. A lot of things went wrong for the Dreamcast right from the start.