I always consider Niagara a more of a hockey market then Hamilton.
I have been aware of the OHL since the mid 70's. The situation in Hamilton has been famine and feast arena wise as far as junior hockey goes. In the 70's the Hamilton arena was a decrepit Forum. The Fincups were at least feasable there and became a great team, winning the Robertson there in 75 I believe. The Forum was a crumbling arena, and the ice plant died, so they hastily moved to the mountain arena, capacity just over 2 grand. Known as a tough crowd Hamilton would have had a constant franchise if they had a decent rink in those days. Eventually Mountain Arena would not pay the bills so the franchise left for a "larger" arena in Brantford.
Too small of a rink for too long and suddenly they build Copps, too big for junior A. I have always believed Hamilton could be a great OHL city, just need the right sized arena. Just as a new rink and sized appropriately opened the doors in St Catherines, the same would happen in the Hammer.
Remember St Catherines lost a team during the 70s as well, the Blackhawks became the Niagra Falls Flyers, so even a great hockey area like the Niagra region does much better with a proper arena.
The whole Golden Horseshoe is a Jr hockey hotbed I would say, I don't think there is much difference between those fans in either town. I have been to both places many times.