The SNES CD addon would probably have just fallen through and Sony would not have made the Playstation so early. I honestly doubt they would have not made a system eventually. They had the resources and knowledge, it likely would have happened whether or not the addon was released.
If Nintendo hadn't made the NES then the video game crash would have subsided much later. Perhaps, never, but once again very unlikely. Another company would have tried it. They may not have been quite as successful, but they would have tried, then other companies would have tried until, eventually, a demographic is established and someone else does it right. That company would likely become much like Nintendo is now. Since they would have to innovate originally to gain interest they would likely stay geared towards innovation if it continued to sell. Some of the great innovations in gaming may have come later than they have, but they would still come eventually.
The DS and Wii would not be failures. It's that simple. The design is impeccable, there is great software support and it is from a company that gamers already know and love. Maybe if the DS and Wii were not the DS and Wii, but then this question makes no sense, therefore is not worth talking about. QED
If Sega never teamed up with MS then maybe the Dreamcast would have lasted longer. :-P Just kidding. It likely would not have lasted as long as it did since there may have been less software support and the resources Sega had for the DC would not have been as great, so it would have been a less impressive system. I don't think Sega teaming up with Microsoft would affect games like Halo 3, but it may have taken longer for them to come about or they would not be as popular.
