There are a few mistakes in your list:
3rd gen
Atari 2600 (1983) 27.64m The Atari 2600 was released in 1977, it's in no way comparable to the systems released in the 1980's, it certainly does not belong in the same "generation" of hardware as the capabilities are not even that similar.
Sega Master System (1985) 10-13m
NES (1985) 61.91m
4th gen
Turbo-Grafx 16 (1989)
Sega Genesis (1989) 29.54 m
SNES- (1991) 49.10 m (The SNES sold for 3 or 4 years after Sega discontinued the Genesis, Nintendo actively promoted it and some of the greatest titles of its lifetime were released after 1994.. most of the extra 20 million systems were sold there)
Now my answer: It depends, your product needs to be compelling enough, a console like the Wii U that came with ports of PS360 games that ran worse than they did on the 6 years old machines cooled down a lot of potential buyers!
The NES was released a while before the Sega Master system, it enabled Nintendo to gain a stronghold on third party contracts and gave them a lot of great exclusives titles...
Also, the xbox 360 was 1 year ahead of the PS3 and it seems like it took a lot of ex Sony customers, with a mix of great early titles and good hardware... now you can argue the PS3 catched on later and the Wii made all this moot, but imagine if the 360 would have been released 2 weeks after the PS3, people would barely know MS released a second console.... so yes.
TL:DR; It makes a difference, but there are many other factors, you have to release something people actually want!
