Jennifer Hudson -- I Got Nothin' For First Lady's 50th Birthday!

Jennifer Hudson was kinda awesome flying into Washington D.C. today ... to perform at Michelle Obama's 50th -- giving a definitive answer on what you get the person who has everything.

Although Michelle will end up with bubkis ... she has solid logic on why she decided to give her assistant a house!

Jennifer says she's gonna rock Michelle's 50th birthday party at The White House with her latest single.