Why, because he's better than Brees, Romo, Brady, and Favre? Anyone who thinks Phillip Rivers is better than Drew Brees, Tom Brady , or even Favre when Favre was on top of his game, is smoking crack.
Rivers has a reputation for blowing big games because his temper gets in his way. Brees, Brady, and Favre all have rings for a reason - and Rivers doesn't have (and never will have) a ring. When rattled, Rivers often loses big games.
Rivers is the Charles Barkley of the NFL.
I'll grant that Rivers is a tough customer and is able to make up for a questionable throwing motion - but he's not in the same league as Brees/Brady.