Yep, people often overlook the snowball effect. If you're selling a good product at a reasonable price then word of mouth alone can drive momentum harder than a billion $ marketing campaign.

Of course, should you be offering something people aren't keen on then it can work against you like a brick to the face ^^; A brick MS were introduced to after the DRM debacle.

In the past that would have been true, but the mobile market has hit handhelds like a train. It's an awful lot easier to compare them to home consoles now, seeing as the 3DS is being regularly outsold by one :p

Genesis did about 30mil, not 40mil. I wrote it wrong initially, so that may change your opinion. It still did relatively well coming out of the NES domination days given that Nintendo sold about 50 million SNES and Sega sold 30 million Genesis.

It's interesting what you pointed out. I didn't know that just "them" saying its good could get people to go out and buy a console. Word of mouth is quite a big things among the less hardcore.

im using the OP's numbers. 

No, he's right. I wrote 39 when I should have written 29 for Genesis. So yeah Genesis did about 30 million rounded while SNES did about 50 mllion. There's about a 20 million gap between them, not 10 as I wrote wrong previously. I've corrected it now.

I can say that the most balanced generation was Wii, PS3 and 360. Ok, Wii was dominating in the first 3 years, than PS3 came back in 2009 with the new Slim Model and started to catch up and surpassing later on in the weekly global numbers. By the way, 360 took the Lead in NA, and PS3 took the lead in Europe and rest of the world. Wii has the global, but it is dying while PS3 still selling enough good, better than WiiU also.

PS4 will do what PS2 did VS GameCube, but One will be better than XBox1, for sure. In the Global PS4 will dominate this gen, and the only place where I can see a battle is NA.

It's just about communication. If there is a well known console everybody want one because everybody has one. Nobody wants to be a outsider and so if a console wins a generation the gap will become even bigger because as I already said: everybody wants one because evertybody has one. Of course it isn't the case but there is the feeling that you want to belong and you follow the mainstream. The Internet says: "Wii U flop. Xbox One fail. PS4 win." Then everybody does it this way.

Only NES , PS1 & PS2 were dominant.

For PS1 & PS2 it played a big role  that cd & dvd format vs nintendo 64 cartidge & gamecube disc had more space availiable for many developers so it had many third party exlusives.

Also one big advantage for sony was that their consoles easily got hacked.

Sega was never a big competitor (only one exception megadrive).

The last generation was actually pretty balanced compared to the 6th generation where the PS2 sold more than 100 million and the GC/Xbox couldn't even sell 30 million!

I might be wrong but I think the Snes beat the Genesis after Sega moved on to the Saturn. Hard to dominate when you aren't playing with anyone else. Basically why my bdsm period was considered a total failure.