The average graphic card could only wish to handle Madden 360. When the "average" graphic card becomes powerful enough to run Madden 360..then you'll start seeing next gen console ports to pc. Right now..a develoer like EA wont port Madden 360/Next Gen to the pc because there isnt a whole lot of sports gamers out there that has a 600 dollar pc graphic card in their pc.
Sure..there are other developers making cutting edge pc games on the pc..but those guys cater more to the niche pc gamer..where EA sports wants instant profit..its just not gonna happen for a few years.