1) N64 failed because the PS was the obvious choice for a System that gen. It used CD's, could play music, had nearly ALL of the 3rd party support to itself. The N64's games also were way too high in price. About $60 - $70 a game. If you adjust for inflation, that would be $90 - $100 a game. For the most part only Nintendo's biggest fans bought the system.
2) GC failed because of its look, mini CD's, lack of 3rd party support, lack of online, and again the PS2 was the obvious choice for the same reasons the PS(1) was. The GC sold less than the N64 because by that time even the N64 owners moved on to PS2. Both the N64 & GC failed due to many other reasons and had almost nothing to do with games themselves.
3) Casuals don't exist IMO. Different people like different games. COD has just as many "casual" fans as Just Dance. Both also have a core following. The only difference between the 2 are how many games they own, and how much time they spend on playing games. There are WAY more "casuals" than core gamers. Without casuals you end up with GC, XB, or PS Vita sales. You only get 50 Million+ with so-called "casual" support.
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