To reiterate NCAA basketball is the dirtiest sport in college. So why would they leave the states when they are getting absurd amount of unregulated money.
College football and college basketball are not going to be dramatically different. Cam Newton was really well compensated, as were several Ole Miss players, etc...
That aside, it's still simpler than that. College athletics are remarkably well funded, to the tune of hundreds of millions annually being spent in excess of revenue. This carries over to the point that it's not just the best development league for NBA and NFL talent, but for almost every sport there is. Just watch the Olympics, there's plenty of these sports in which people can go pro, yet athlete after athlete, from all over the world mind you, went to various colleges in the United States. The best athletes in most sports, from all over the world come through college athletics here.
That's not coincidence, they come here for a reason, even if they're not getting paid. It is because the resources being made available to them are superior to what they get elsewhere, it is as simple as that in many cases. If you want to see the flip side, take a look at the Ball brother's catastrophic European tour. That's what it looks like when guys decide to ditch the college route.
Saban actually made some statements earlier about people leaving college too earlier, how that's not a good business decision. Think about it the other way, what happens if you go the Ball brothers route? You end up competing with more experienced players, and you look inept and over your head. College athletics actually incubates and protects these guy's development. The constant players leaving due to lack of eligibility (and yes some going pro early) creates a churn that opens up playing time. That doesn't exist in professional leagues where a career can exceed 15 years and where you're not just competing against teenagers and people in their early 20s, but against veterans.
Think about all the 5 stars that went to Alabama that were not an immediate successes, what happens in the XFL? They'd wash out immediately, having lost their amateur status and then what? How many guys are going to gamble their entire careers on that? Not too many, because they're going to make good business decisions for the most part.
I'll try not to derail this further, but the some of the same things that undid the AAF are also why forgoing college for these sort of leagues is not a good idea (and not necessarily something the NFL wants, I think I alluded to some of these things a while ago in the other thread). They have more fans, they can outspend these semi-pro leagues, and they are far better at creating superstars.