There's never been a definite size given, but it's generally accepted that he's around two hundred meters tall, which is about the same size as modern Godzilla. So, no, Cthulhu is not bigger than the Matriarch.
*It's not very effective* *It's also super effective* *let's split the difference and call it normal effectiveness, okay?* CTHULHU HP - 9900/9999 Cthulhu used DRIZZLE.
It started to rain in the Matriarch! Team Magma Admin Gravity withdraws Jolteon. Team Magma Admin Gravity sends out Aegislash!
Staple-staple, I've got one, Staple-staple, First to sum, Staple-staple, Come to mum, Staple-staple, Here I'd come.
*pulls out Impossible Poke Ball* "GO, SUPER SPACE CYBER-ZOMBIE CTHULU!!" NO, RAINBOW DASH!! YOU'LL KILL US ALL!!!
*Cthulu holds up a finger in protest* PARDON ME, GOOD SIR, BUT WHAT IN THE NAME OF ALL THAT IS VILE AND UNHOLY IS THAT SUPPOSED TO BE?