The Arsenal boss has come under fire from some sections of the footballing world, with his side having fallen away from the Premier League title race despite being top at one point during the campaign.
"He's not everybody's cup of tea but the one thing you must say is his teams play a fantastic way and he's proved to be one of the greats as far as I'm concerned," said Bruce, according to BT Sport.
"He's not had the spending power of the big, huge clubs in Europe but he's always been competing - semi-finals, finals, the final of the Champions League.
"With his record how we're even questioning him baffles me."
Arsenal currently occupy fourth position in the Premier League table.