Agree - it's the tires followed by your contact points with the bike (seat, seatpost, handlebars, etc...) that can do a lot for the ride. That said, if the frame is uber stiff then that's a problem but working the other components can do a lot to mitigate that stiffness. And I also agree with others on the point that the frame material matters little compared to the design and geometry. You can make a stiff or noodle frame out of any material.

J.