I am not sure why you are telling me about the bang for the buck thing, sure 5 games for the price of one is really cool but more people are willing to buy the 1 new expensive game than 5 older ones.
Look about the 3D part here is what. Not just that a game is in 3D it is better, 3D can be bad. But done right it will be superior to 2D. I am trying to make a comparison, think of audio tape and CD's. If a song was on a CD, but the simplest scratch will make it skip and if the CD medium hangs up a lot even if it has higher quality sound , perfectly working tapes are better. But if the CD is durable, and the quality of the songs play for hours with no damage done then it is better than the audio tapes. I hope you got the idea. 3D is like a monster next to 2D, it just opens a whole new, how can I say this, dimension?
I know they are the same people that make Hannah shatter The Beatles but what are you going to do? This is mainstream and companies exist to serve them and take their money, and whatever they want they will do. This is why 2D is not the main thing any more .
Story IS the single most important aspect of a videogame
but while that is an opinion
Fighters and platformers can be proven by numbers. We all know that Mortal Kombat and Street Fighters were enough reasons to buy a genesis/snes back then. People were dying for an exact arcade port. Platformers were mainstream with Sonic and Super Mario are system sellers. How many platformers are out there today? I asked this question the other day here and some one told me they were replaced by the likes of Ninja Gaiden and Devil May Cry. So are fighters , they are not main stream they definitely lost their place. How many new fighter IPs have we seen lately? I am guessing the newest is Soul Caliber.
You have to agree the greatest thing out there now are 3rd person adventure(GTA, Zelda) FPS(Halo, Killzone, COD), and Guitar Hero .