luda had 5 consecutive plats AND bodied that nikka on stomp 

Where's that decline you're speaking of, Trouble Man was his best album since King and went gold pretty easily, and he just had a nice feature on the biggest single of the last couple months. He's still a good rapper, and he's still succesful.
this. paper trail was tips vol 2 hard knock lifePaper Trail >>>>> Trouble Man easily
Five consecutive platinum albums (Trap Muzik, Urban Legend, KING, T.I. vs. T.I.P., Paper Trail)
One gold album (No Mercy)
One album on its way to being Gold (Trouble Man)
Numerous hit songs
Currently featured on the biggest song of 2013 and is on its way to having the longest run @ #1 in years
^^^ Those are undeniable facts. I don't necessarily consider anyone being "king" of anything to be based on quality. That's not even what the title implies especially since quality is subjective. The fact is there's maybe two other Southern solo artists who have dominated like T.I. Lil' Wayne and Ludacris are the only other contenders in that sense and may even surpass T.I. in that sense.