Bale, the world's most expensive footballer, reasserted his value with a hat-trick in a 4-0 rout of Valladolid on Saturday, scoring with his head and either foot.
The ex-Tottenham attacker's efforts prompted comparisons with teammate Ronaldo, who missed the game through injury.
However, Marcelo feels Ronaldo remains unchallenged as the club's top act.
Marcelo told reporters: "You cannot compare Bale and Ronaldo. Cristiano is above the rest of the players and everyone on the team knows that. Bale is a great player, though, and he is on the right track."
The 25-year-old added of last night's game: "Every game is difficult and Valladolid did not allow us to play at first, but then we got well set defensively and offensively.