what she means:
in Friends, Chandler was always considered very average and not that attractive, in fact the very base of his character was that he was the funny/goofy one, Ross was the smart one, and that Joey was the cute one, but Chandler was actually remarkably intelligent and hardworking, as well as the fact Matthew Perry was a very attractive man, whereas Ross most often got himself into awkward shenanigans and Joey was often very goofy. Chandler was the best of all three of them put together, without some of the other two's worse attributes (Ross' tendency to ramble on, Joey's grudge-holding, Ross' quick temper, etc), yet somehow it was considered by pretty much everybody in the Friends universe that Monica was a catch for Chandler and he should feel honoured to be dating her... Chandler was a brilliant character and it is unacceptable that his most prominent attribute, his comedy, has become recognisably his only positive attribute.
“Look, uh, if you’re gonna be moving in with him I feel it’s my responsibility to tell you the truth about him! Okay? He’s a terrible roommate! Terrible! He uh, forgets to umm… Oh-oh he always, he always umm. Oh, who am I kidding! He’s the best roommate ever!”