I saw this news on a local newspaper so I started lookig it up.
It's neither Messi or Cristiano Ronaldo, these two are the best paid players but the richest one is Faik Bolkiah the 19 year old nephew of the Sultan of Brunei, he was playing for Leicester and has also been in other English teams, and he's not even on the main team he is on the development squad.
Also I looked up the Leicester FC site and he is mentioned as having been there up to July of last year, I really don't know if he's still there as I didn't see his name on any of the rosters they have on the site, perhaps he moved back to Brunei, where by the way he has played for the national team and has scored a few goals with it.
His personal wealth is estimated at 20 billion USD, so Messi and Cristiano are going to have to be playing for a long time to equal his wealth