Backstreet Boys' Brian Littrell -- My House is More Baller Than You Think

Backstreet Boy Brian Littrell is sticking it to everyone hating on the tiny West Hollywood home he just sold -- cause it was only a back-up ... to his PHAT MANSION!!

Turns out Brian and his wife are also sitting on a 15,000 square foot palace in Georgia that's straight outta "Gone with the Wind" -- but better, 'cause this place has a lake, a recording studio AND tennis court.

Still don't hate your life? It also has 5 bedrooms, 7 bathrooms ... on 39 FREAKIN' ACRES!!

Brian's wife Leighanne says they only sold the WeHo spot because they weren't going to be there for months at a time.

Why would they be?