only one really matters, and that's not enough great exclusive games. Dream Cast, X-Box, 3DO, and every other console that failed or will fail.
Dreamcast? Are you shitting me? That's the one console in memory that launched with a solid library of good and diverse games, and those were almost all exclusive since the system had nearly a year to itself. It was only when developers realized - quickly- that the DC wasn't going to last long that many of their games ended up going to other systems - usually the PS2 - but even then it was months after they first launched.
Dreamcast was killed for 2 related reasons:
1) Sega's mishandling of the Genesis and Saturn completely undermined consumer confidence in the brand. This allowed...
2) Sony's rise to take Sega's place. By the time the DC was announced, Sony had built a strong following, and soon after it was promising the most bestest, most powerfulest console ever. Sure it was mostly bullshit, but I knew dozens of students who wouldn't give the DC a sniff because "PS2 is coming, and it is gonna be AWESOME!" Didn't matter that it launched at a high price with one decent game, making it a glorified DVD player for it's first year. The PR worked, and kept people away from the DC.