According to an index developed in 2015, Earth is not the most habitable planet found yet.
Kepler-442b, a rocky near-Earth-sized exoplanet that is 1206 light-years away from Earth, has a rating of 0.836. On the other hand, Earth has a rating of 0.829.
The paper introducing the habitability index clarifies that a higher-than-Earth value "does not mean these planets are 'more habitable' than Earth", as the actual habitability is uncertain due to Kepler-442b's atmosphere and surface being still unknown.