It's all in the $$$ man. Developers create whatever sells. The sales of rehashes means most people can't wait to buy the next one.
@ OP
I can't believe you didn't mention the Guitar hero franchise. At least, animal crossing waited 6 years and cod waited a year before their rehashes. How many GH games are there now and whats the difference?
"Dr. Tenma, according to you, lives are equal. That's why I live today. But you must have realised it by now...the only thing people are equal in is death"---Johann Liebert (MONSTER)
"WAR is a racket. It always has been.
It is possibly the oldest, easily the most profitable, surely the most vicious. It is the only one international in scope. It is the only one in which the profits are reckoned in dollars and the losses in lives"---Maj. Gen. Smedley Butler
