AJ McLean Says Backstreet Boys Not Signing With Shaq Was 'Right Decision'

The Backstreet Boys made the "right decision" not signing with Shaquille O'Neal back in the day ... so says AJ McLean, who tells TMZ Sports while he adores the NBA legend -- he doubts they'd have the same success had they inked a deal with him.

It's a wild story, but 100% true -- both BSB and *NSYNC used Shaq's Orlando studio to record some of their earliest music when he was a member of the Magic in the '90s ... and O'Neal has openly expressed his regret over not pouncing on the opportunity to work with the boy bands in an official capacity.

We caught up with AJ recently ... and asked a good ol' "what if?"

Safe to say both groups did just fine ... and AJ wondered how things would have looked had they joined forces with the Hall of Famer -- and if they'd still be one of the most iconic groups to ever grab the mic.

"No disrespect to Shaq, because I love him to death, but don't think we'd be where we are today necessarily," he said.

AJ noted everything Shaq touches turns to gold off the court, as the big man's got an extensive and lucrative business portfolio ... but this is one that all worked out in the end.

"I think we might have made the right decision," AJ added.

It's interesting ... 'cause *NSYNC member Lance Bass told us a few years back he wishes Shaq would've been part of their team ... even though he wouldn't have been able to box out Lou Pearlman entirely.