The 77-year-old movie mogul, who took charge of 14 Academy Awards shows between 1990 and 2008, was dead found in a parking lot in L.A. last October (11).
Cates' famous friends and colleagues gathered on Monday to remember him at a memorial held at the Directors Guild of America headquarters, and Hanks was among the speakers at the service.
The Philadelphia star told the crowd, "He was the great embodiment of joy in this business. He was so much fun to be around."
Crystal, who is hosting the 2012 Academy Awards, dedicated the upcoming show to his late pal, stating, "We did six Oscar shows together or 312 hours of live TV... This show, it will be for you."
Bening also spoke about working with Cates, revealing she struggled to resist when he called her with a last-minute plea for assistance, adding, "He'd always say, 'I'm only calling the busiest people', which was brilliant. How could you say that you were too busy?..."
Josh Groban also performed in his honour and later took to his Twitter.com page to pay his respects, writing, "I sang at Gil Cates's memorial service tonight. He was a great guy who did wonderful things for the arts in LA and around the world."
Other guests included John Lithgow and Ted Danson, according to Variety.