I have vague memories of watching him play, but he was way past his prime. I watch a lot of classic games and I LOVE the history of the game, so I'll bite.
Gordie wasn't a gym guy. He was farm tough, cold weather tough, and determined. Hard as a piece of iron. I met him once when he was in his 60s and his handshake felt inhuman, like putting your hand in a vice. Funny thing, though, he was a lot shorter than I expected. He was listed at slightly over 6 feet, but I'd say he was 5'10'. But a powerful, powerful man with a neck like a tree trunk.
He did not strike me as an overly intelligent man (i don't mean that in a cruel way, he was just not overly articulate), but he was older so he may have been in cognitive decline. But on the ice he had great hockey sense, and coupled with an unprecedented level of grit and determination, he went through people. He played as long as he did simply because he wanted to. He defied normal human physical decline.
Most people that talk about Gordie explain his greatness in those terms, not in his pure goal scoring or puck handling ability. Different time, different game, but he was the hardest man in an era of hard men, which made him legendary.