This is a claim often made by Hellfire preachers. One that has me thinking there must be a Fifth Gospel I'm not familiar with. I've never seen them give a mathematical breakdown of how that claim is accurate.
Part of the problem here may of course come from people forgetting contemporary Heaven is NOT the paradise we're looking forward to, we're looking forward to the New Heaven and New Earth.
Jesus talked about the Kingdom constantly, it's in mind in almost every speech He gave, including the ones about Hell. He definitely talked about it way more then Hell, even if we include the Outer Darkness references that I disagree with interpreting as about Hell.