Because CoD, GTA and Halo are niche...

One of the very first video games called "Spacewar" made in 1961 at MIT used guns. The game was two space ships flying around shooting each other. Yes, the first multiplayer shooter is almost 50 years old, or at least twice the average age of people on this board.

It's a rail shooter, they don't count

None of these franchises appear in the top 10 of best selling games. Duck Hunt is the only shooter that does.  (the top 20 includes GTA, and the Top 30 includes Starcraft)

When 9 of the 10 most popular games ever are not shooters, it probably indicates that shooters are not the standard, but the minority. 

I wish we would have another word for that...

The desire to appeal to the American market.

Just because they are not in the all time top 10 does not mean they are niche.

I suppose NSMB is niche, then? It's only 11th.

I was talking about genres, not individual games.

Every minority audience is niche, by definition. 

"A niche market is the subset of the market on which a specific product is focusing on"

Every single product that is on sale can be defined by its niche market.

http://en.wikipedia.org/wiki/Niche_market

Technically, even the whole video game industry is built a niche, the "gamers". 

I thought it was obvious that in this case, I was talking about a smaller niche of the gamer demographic.

Don't know which games are in the top 10 but I would suspect there are a few old Pokemons, Marios and Wii Sports.  Apart from Wii Sports they would generally be old games.  I think his question is when did guns become the standard.  They were not previously but they certainly are now.  If you look at the top 10 games of this year apart from the Nintendo games they will all have games.  Likewise for 2008.  So it is hard to say guns aren't standard in games.  They most certainly are in the big HD games other than Forza and GT5.

The top 20 is dominated by Nintendo. Mostly NES-SNES, but quite a bit of DS-Wii sneaking in there. San Andreas is the first non-Ninty game, at 13th.

But games on the whole don't tend to sell that much anymore, with the exception of massively appealing casual games and perhaps 2D/Kart Mario.

Guns dont kill people...video games do.