Despite both players being tied on a record-breaking 41 league goals for the season, Xavi believes that Messi has the edge over his Portuguese rival.
"Obviously Cristiano is a great footballer," he told Gol TV. "They are two players who make the most difference on a football field, but Messi is above anyone.
"I hate to compare, but Leo gives us everything - scores goals; creates them; always involved in the flow of the game, leading nearly every attacking move.
"This guy has it all: he even heads the ball well in spite of his height. [Barca coach Pep Guardiola] once said that he dominates every facet of the game, and he is absolutely right. He is the best, number one."
The Catalan club can cut Madrid's lead at the top of La Liga to a single point with a win at the Nou Camp this weekend.