Time for a basic question.

What, above all else, sells a video game system? Price? A killer title? A great library?

This is a general question. Feel free to use any generations to support your answer.

I don't think it's any of those.

I think it's the best use of hardware. People loved how the PS1  played on discs, they loved how the PS2 could play DVDs and was one of the cheapest DVDs on the market (especially in Japan, where I think it was significantly cheaper than any other DVD player, but I could easily be wrong about this).

And people loved the motion controls in the Wii.

I'm really caught between that and thinking that the "Killer app" is the #1 choice. Look at Halo, look at Wii Sports. The other great games will follow once the big boom sets the stage and grabs the attention.

I may come back to revise my choice later, but ima go ahead and throw this out for now to spark a discussion.

HYPE AND MARKETING.

Then PRICE AND GAMES

I actually think its just that people's needs change over time. The system that meets those needs sells the best - trust in the wisdom of the masses. I don't think you can objectively say people suddenly got stupid going from NES/SNES to PS1/PS2 to Wii at whatever junction.

These days people are far busier than they were even five to ten years ago, and so short, super fun experiences are now huge. I can't really think of any single player games that are doing banner numbers for instance. If you look at the current market, I think the one thing Wii & X360 have in common is that they are both excellent at multiplayer and have games that can be played in short sessions but are fun. PS3 has some too, but not nearly as many as the others.

Even Nintendo's top stuff pretty much is all multiplayer now - NSMB Wii / Galaxy 2 have co-op modes, DKC & Kirby will too. Obviously Brawl, Halo, Mario Kart, Call of Duty are sort of the "online kingpins" of the generation. Pokemon and GTA are moving towards more and more multiplayer as well. Even more obviously stuff like Wii Sports, Wii Fit, Wii Fit Plus, WSR, Wii Party, Mario Party, Mario & Sonic, and Just Dance benefit from multiplayer too (even if its experiental multiplayer vs. true multiplayer). Single player experiences on the HD systems now seems like a side "mode" rather than what the developers want you to play. Other than some titles from Nintendo with hardened fan bases like Zelda or Fire Emblem, single player experiences seem to be in pretty steady decline, and other than tactics and pricing, I think thats one of the big reasons PS3 is still in third place. PS1 / PS2 to me was always three markets: Shovel Ware, Single Player Action Games, and New Genre / Big Exclusives. Shovel Ware is on Wii, so thats a third of the PS1 / PS2 market, Single Player Action is in decline, but still on PS3 to some degree, and new genre / big exclusives have moved to Wii or been split between PS3 / X360.

sells it to people in general... or to me?

I would say a killer title, I'm almost certain that the Wii wouldn't have sold quite as much without the likes of Wii Fit, Wii Sports and NSMBWii.  Same with the DS and Brain Training, Nintendogs and Dragon Quest IX

Look at the Wii price cut - initially, while it moved a little hardware, it was nothing stellar. Then NSMBWii came out. So I'd say it's a combination, but price without the accompanying software won't work well, software is more important. You can also see it all year long for the Wii - when there's software, sales are better, when there's none, sales are less. Compare Wii Year to Year. Some periods this year Wii did less well than last year even though the price is lower (no software), some periods it did better (presence of software).

Hype and marketing is the answer.

Software comes in 3rd. Price is at a distant 4th.

Both of those things

But yeah hype and marketing is EXTREMELY powerful

Hype and Marketing of the PS2 single handedly almost killed the Dreamcast.......magazines had front covers saying, "FIRST LOOK at the amazing PS2"

With PS3 there was nothing but negativity near its launch.

I can't answer this question without pondering on the PlayStation2.

I think, to a minor extent, it is a number of factors including entry price, a software library defining the "experience," marketing, big name titles and on.

Learning from the PS2, I am convinced it comes down to multi-media functionality with a new technology that is becoming mainstream just as the system is being released. Case in point, the PS2 was released just as consumers were transitioning from VHS to DVD. Henceforth, they could kill two birds with one stone:

1. Their family's gaming wants and 2. The parent's home movie viewing wants

Well what about the PS3? The PS3 with Blu Ray when it was launched failed in anticipating the world-wide adoption time from DVD to blu ray. They overshot by about 5 to 10 years. Just reading from VGChartz posts, Blu Ray still has only about 10 to 12% of the home movie market and the technology has been around for coming on 5 years now. The PS3 even currently is ahead of it's time, which will be good when we are old and reminiscing, but being ahead of your time does not pay the bills for the development costs.

So for me, it comes down to multi-media functionality that advantageously employs new technology just becoming mainstream.

Mainstream and widely adopted I considered synonymous.