Why he cant just generate indefinite amount of bitcoins for him and exchange it to real cash, right?
The part above of OP is just stupid, but the comparison of Satoshi to Bill Gates is interesting. I strongly suspect there isn't one person who is Satoshi, that it was a collusion of government agencies who came up with bitcoin in an effort to ensnare tax evaders. Don't put anything past those barstards. Who would pass up a Bill Gates-sized pile of cash? Answer: No one in their right mind.
And yet Satoshi's coins haven't moved that I know of. Unless he's dead
He may have just lost the keys
Or intentionally destroyed them soon after he had started mining his stash of coins (or even before that). Whether he regrets his decision now is another question, though. I guess it could well be the reason why he vanished into nothingness and obscurity. That is, he destroyed his keys since he didn't believe in Bitcoin himself (remember the days of 10k dollar pizza?), but when Bitcoin kicked off for real, he felt very disappointed with himself and decided to forget about Bitcoin (and his lost millions) altogether. As the saying goes, out of sight, out of mind