I personally believe that the gameplay jump from PS2 to PS360 was drastic. Worlds became significantly more interactive, AI was drastically improved, physics became a lot more realistic. In addition performance drastically refined the old gameplay.
Just by thinking of all the Uncharted games, thats a next gen jump in all fronts.
KZ2's AI and animations was a whole new world compared to any FPS we got the generation before it.
Bioshock refined the FPS experience and blended beautifully visuals and gameplay that the gen before it wouldnt be able to
perform adequately in order to offer a solid experience. The elemental forces finally could have been presented and interacted with in a manner that they could play a significant role on the gameplay mechanics (ice, fire, electricity, wind, water etc)
Gran Turismo 5 brought us realism that was totally impossible on the PS2. Not just in the visual department but on the gameplay too. The physics, weather conditions, day time transitions were a huge leap from the older games.
The visuals themselves in the transition to PS360 made the games a whole lot more immersive which impacted the gameplay experience. For example Bioshock wouldnt have been possible to convince the underwater, claustrophobic atmosphere on a PS2
I can name more examples but the list would be too big and I am bored.
This gen though offered nothing of the sorts so far except a refined visual presentation. Even the most promising games announced so far dont clearly show a generational improvement of experience. Quantum Break is probably the only game for me that is closer to fulfilling that promise. Oh and one other game. Metal Gear Solid 5 ironically is crossgen yet it manages to convince me.