Barcelona lead Madrid on goal difference at the top of the table on 34 points, with Sevilla three points back in third.
However, just three points separate fourth-place Real Sociedad on 27 points and Granada in ninth.
Barcelona have lost three and drawn one of their 15 games this season, while Madrid have drawn four and lost one.
Messi thinks it displays that the strength of the teams across the league has improved.
"Everything is becoming more and more even," the Argentina forward said at an Adidas media event on Wednesday.
"They have been for several years and we notice that there is more equality, that any team beats any other team, which is increasingly difficult to play as an away team.
"The teams have become stronger at home because they know that in order to achieve their goals they must do it well at home.
"This makes everything more equal and more complicated."
Messi has one eye on El Clasico with Madrid on December 18 and has no doubt the fixture will once again be pivotal in the title race.
"I expect a very strong Real Madrid," Messi added. "They have shown it in the last matches, in LaLiga and in the Champions League.
"Barca v Madrid and Madrid v Barca are always special matches. It doesn't matter how the teams arrive, although it's true that we both go into it at a good time."