It also attributes to the type of life he lives.

Mayweather is trying to become a mainstream name by doing the things he's been doing. Cotto could be just as big, but he only becomes news when he's about to fight because he probably lives a normal life. Hatton is the same way. HUGE in England, but the most excitement out of boxing you get out of him is his liking to beer and food. I could name more fighters but all-in-all everyone leads pretty normal lives outside the ring.

Pacquiao on the other hand does movies, goes clubbing, makes music, delays training and appearances, supposedly cheats on his wife, etc. There's a lot of room for error with his lifstyle considering he's a boxer. Look at Tyson! He lived a crazy life outside of boxing and that's why he was always on the spotlight.

It's basically just easy to write stuff about Manny because there's so much excitement with him in the ring AND outside of it.